Delete (cruD) using Ruby-OCI8

In this post, we’re going to take a look at the D in CRUD: Delete.

We use the ruby-oci8 driver to delete some data in the database tables, using the connection object created in the Initial Setup section of the first post in this series.

PLEASE REVIEW ALL EXAMPLE CODE AND ONLY RUN IT IF YOU ARE SURE IT WILL NOT CAUSE ANY PROBLEMS WITH YOUR SYSTEM.

Helper Function

My helper function get_all_rows() encapsulates a select statement used to verify that the deletes worked. The select functionality is covered in the R part of this series, so I won’t go into the details here.

def get_all_rows (label, data_type = 'people')
 connectString = ENV['db_connect']
 con = OCI8.new(connectString)

 # Query all rows
 statement = 'select id, name, age, notes from lcs_people order by id';

 if data_type == 'pets'
   statement = 'select id, name, owner, type from lcs_pets order by owner, id'
 end

 cursor = con.parse(statement)
 cursor.exec
 printf " %s:\n", label
 cursor.fetch() {|row|
 if data_type == 'people'
   printf " Id: %d, Name: %s, Age: %d, Notes: %s\n", row[0], row[1], row[2], row[3]
 else
   printf " Id: %d, Name: %s, Owner: %d, Type: %s\n", row[0], row[1], row[2], row[3]
 end
 }
 printf "\n"
end

Add this function to the top of your file.

Resetting the data

To keep the examples clean and precise, I will reset the data at times.

Create a new file called reset_data.rb with the following code and run it whenever you would like to reset the data. (Notice this version adds people and pet data not included in other sections.)

require 'oci8'
connectString = ENV['db_connect']
con = OCI8.new(connectString)

# Delete rows
cursor = con.parse("delete from lcs_pets")
cursor.exec

# Reset Identity Coulmn
cursor = con.parse("alter table lcs_pets modify id generated BY DEFAULT as identity (START WITH 8)")
cursor.exec

# Delete rows
cursor = con.parse("delete from lcs_people")
cursor.exec

# Reset Identity Coulmn
cursor = con.parse("alter table lcs_people modify id generated BY DEFAULT as identity (START WITH 8)")
cursor.exec

# Insert default people rows
cursor = con.parse("INSERT INTO lcs_people(id, name, age, notes) VALUES (:id, :name, :age, :notes)")
cursor.max_array_size = 7
cursor.bind_param_array(:id, [1, 2, 3, 4, 5, 6, 7])
cursor.bind_param_array(:name, ["Bob", "Kim", "Cheryl", "Bob", "Stacey", "Pete", "Pat"])
cursor.bind_param_array(:age, [35, 27, 23, 27, 45, 23, 36])
cursor.bind_param_array(:notes, ["I like dogs", "I like birds", "I like horses", "I like rabbits", "I like snakes", "I like cats", "I like dogs"])
people_row_count = cursor.exec_array
printf " %d people rows inserted\n", people_row_count

# Insert default pet rows
cursor = con.parse("INSERT INTO lcs_pets(id, name, owner, type) VALUES (:id, :name, :owner, :type)")
cursor.max_array_size = 7
cursor.bind_param_array(:id, [1, 2, 3, 4, 5, 6, 7])
cursor.bind_param_array(:name, ["Duke", "Dragon", "Sneaky", "Red", "Red", "Buster", "Fido"])
cursor.bind_param_array(:owner, [1, 2, 5, 2, 3, 1, 7])
cursor.bind_param_array(:type, ["dog", "bird", "snake", "bird", "horse", "dog", "cat"])
pet_row_count = cursor.exec_array
printf " %d pet rows inserted\n", pet_row_count

con.commit
Boilerplate template

The template we will be using is:

require 'oci8'
connectString = ENV['db_connect']

def get_all_rows (label, data_type = 'people')
 connectString = ENV['db_connect']
 con = OCI8.new(connectString)

 # Query all rows
 statement = 'select id, name, age, notes from lcs_people order by id';

 if data_type == 'pets'
   statement = 'select id, name, owner, type from lcs_pets order by owner, id'
 end

 cursor = con.parse(statement)
 cursor.exec
 printf " %s:\n", label
 cursor.fetch() {|row|
 if data_type == 'people'
   printf " Id: %d, Name: %s, Age: %d, Notes: %s\n", row[0], row[1], row[2], row[3]
 else
   printf " Id: %d, Name: %s, Owner: %d, Type: %s\n", row[0], row[1], row[2], row[3]
 end
 }
 printf "\n"
end

con = OCI8.new(connectString)

get_all_rows('Original Data', 'pets')

# Your code here

get_all_rows('New Data', 'pets')

For each exercise, replace the “# Your code here” line with your code.

Reset the data

First, let’s run reset_data.rb to set up our data.

Simple delete

We will perform a simple delete that removes a single record from the lcs_people table.  These are the steps performed in the code snippet below.

  • Prepare a SQL DELETE statement, deleting the record with an id of 1.
  • Parse the statement to create a cursor.
  • Bind the id value.  (See the R part of this series for an explanation of bind variables.)
  • Execute the statement.
  • Commit the transaction.
statement = "delete from lcs_pets where id = :id"
cursor = con.parse(statement)
cursor.bind_param(:id,1)
cursor.exec
con.commit

When I run this code in my Ruby session, I see:

 Original Data:
 Id: 1, Name: Duke, Owner: 1, Type: dog
 Id: 6, Name: Buster, Owner: 1, Type: dog
 Id: 2, Name: Dragon, Owner: 2, Type: bird
 Id: 4, Name: Red, Owner: 2, Type: bird
 Id: 5, Name: Red, Owner: 3, Type: horse
 Id: 3, Name: Sneaky, Owner: 5, Type: snake
 Id: 7, Name: Fido, Owner: 7, Type: cat

 New Data:
 Id: 6, Name: Buster, Owner: 1, Type: dog
 Id: 2, Name: Dragon, Owner: 2, Type: bird
 Id: 4, Name: Red, Owner: 2, Type: bird
 Id: 5, Name: Red, Owner: 3, Type: horse
 Id: 3, Name: Sneaky, Owner: 5, Type: snake
 Id: 7, Name: Fido, Owner: 7, Type: cat
Extra Fun 1

Delete all the birds.

Your results should be:

 Original Data:
 Id: 6, Name: Buster, Owner: 1, Type: dog
 Id: 2, Name: Dragon, Owner: 2, Type: bird
 Id: 4, Name: Red, Owner: 2, Type: bird
 Id: 5, Name: Red, Owner: 3, Type: horse
 Id: 3, Name: Sneaky, Owner: 5, Type: snake
 Id: 7, Name: Fido, Owner: 7, Type: cat

 New Data:
 Id: 6, Name: Buster, Owner: 1, Type: dog
 Id: 5, Name: Red, Owner: 3, Type: horse
 Id: 3, Name: Sneaky, Owner: 5, Type: snake
 Id: 7, Name: Fido, Owner: 7, Type: cat
Answer
Reset the data

Now is a good time to run reset_data.rb.

Boilerplate change

Change the boilerplate get_all_rows statements to get people and pet data.

get_all_rows('Original People Data', 'people')
get_all_rows('Original Pet Data', 'pets')

# Your code here

get_all_rows('New People Data', 'people')
get_all_rows('New Pet Data', 'pets')
Deleting records referenced by Foreign Keys

If you are using integrity constraints in your database (of course you are, because then you let the database do some heavy lifting for you), you will sometimes need to change the way you process your changes.

In our design, we have a Foreign Key constraint in lcs_pets that ensures if a pet has an owner, that owner exists.

This is the statement that creates the constraint in the Creating the Database Objects section of the Initial Setup post.

ALTER TABLE LCS_PETS ADD CONSTRAINT FK_LCS_PETS_OWNER FOREIGN KEY ("OWNER") REFERENCES "LCS_PEOPLE" ("ID")
/

If we attempt to delete a record in lcs_people that is referenced in lcs_pets (Person has a pet,) we get an error.

statement = "delete from lcs_people where id = :id"
cursor = con.parse(statement)
cursor.bind_param(:id,1)
cursor.exec
con.commit

When I run this code in my Ruby session, I see:

stmt.c:243:in oci8lib_230.so: ORA-02292: integrity constraint (BLAINE.FK_LCS_PETS_OWNER) violated - child record found (OCIError)
 from /home/bcarter/.rvm/gems/ruby-2.3.1/gems/ruby-oci8-2.2.2/lib/oci8/cursor.rb:129:in `exec'
 from delete2.rb:36:in `<main>'

Before deleting the person you have to handle the pet (watch out for claws and teeth).

There are a few options here, depending on your database design:

  • If: pets are not required to have an owner and you only want to delete the person, not the pets.  Then: you can update the pets and set their owner to null.
  • If: pets are required to have an owner.  Then: you can delete the pets for the owner.

In either of the above scenarios, you can update the pets and set their owner to another person.

Bob is moving out of our area and his new apartment doesn’t allow pets, so he’s giving them to Kim.  Let’s use that last option here.

  • Prepare a SQL UPDATE statement, changing owner to 2 (Kim) for the records with an owner of 1 (Bob).  Updating is covered in the U part of this series.
  • Parse the statement to create a cursor.
  • Bind the new and old owner values.
  • Execute the statement.
  • Prepare a SQL DELETE statement, deleting records with an id of 1 (Bob).
  • Parse the statement to create a cursor.
  • Bind the id value.
  • Execute the statement.
  • Commit both transactions.
statement = "update lcs_pets set owner = :newOwner where owner = :oldOwner"
cursor = con.parse(statement)
cursor.bind_param(:newOwner,2)
cursor.bind_param(:oldOwner,1)
cursor.exec

statement = "delete from lcs_people where id = :id"
cursor = con.parse(statement)
cursor.bind_param(:id,1)
cursor.exec
con.commit

When I run this code in my Ruby session, I see:

 Original People Data:
 Id: 1, Name: Bob, Age: 35, Notes: I like dogs
 Id: 2, Name: Kim, Age: 27, Notes: I like birds
 Id: 3, Name: Cheryl, Age: 23, Notes: I like horses
 Id: 4, Name: Bob, Age: 27, Notes: I like rabbits
 Id: 5, Name: Stacey, Age: 45, Notes: I like snakes
 Id: 6, Name: Pete, Age: 23, Notes: I like cats
 Id: 7, Name: Pat, Age: 36, Notes: I like dogs

 Original Pet Data:
 Id: 1, Name: Duke, Owner: 1, Type: dog
 Id: 6, Name: Buster, Owner: 1, Type: dog
 Id: 2, Name: Dragon, Owner: 2, Type: bird
 Id: 4, Name: Red, Owner: 2, Type: bird
 Id: 5, Name: Red, Owner: 3, Type: horse
 Id: 3, Name: Sneaky, Owner: 5, Type: snake
 Id: 7, Name: Fido, Owner: 7, Type: cat

 New People Data:
 Id: 2, Name: Kim, Age: 27, Notes: I like birds
 Id: 3, Name: Cheryl, Age: 23, Notes: I like horses
 Id: 4, Name: Bob, Age: 27, Notes: I like rabbits
 Id: 5, Name: Stacey, Age: 45, Notes: I like snakes
 Id: 6, Name: Pete, Age: 23, Notes: I like cats
 Id: 7, Name: Pat, Age: 36, Notes: I like dogs

 New Pet Data:
 Id: 1, Name: Duke, Owner: 2, Type: dog
 Id: 2, Name: Dragon, Owner: 2, Type: bird
 Id: 4, Name: Red, Owner: 2, Type: bird
 Id: 6, Name: Buster, Owner: 2, Type: dog
 Id: 5, Name: Red, Owner: 3, Type: horse
 Id: 3, Name: Sneaky, Owner: 5, Type: snake
 Id: 7, Name: Fido, Owner: 7, Type: cat

When you change data it’s a good idea to verify the number of affected rows.  This is covered in the R part of this series.

Extra Fun 2

Due to a zoning change, snakes are no longer allowed in our area.  Stacey has decided to move and take Sneaky with her.

Let’s fix our data.

Your results should be:

 Original People Data:
 Id: 2, Name: Kim, Age: 27, Notes: I like birds
 Id: 3, Name: Cheryl, Age: 23, Notes: I like horses
 Id: 4, Name: Bob, Age: 27, Notes: I like rabbits
 Id: 5, Name: Stacey, Age: 45, Notes: I like snakes
 Id: 6, Name: Pete, Age: 23, Notes: I like cats
 Id: 7, Name: Pat, Age: 36, Notes: I like dogs

 Original Pet Data:
 Id: 1, Name: Duke, Owner: 2, Type: dog
 Id: 2, Name: Dragon, Owner: 2, Type: bird
 Id: 4, Name: Red, Owner: 2, Type: bird
 Id: 6, Name: Buster, Owner: 2, Type: dog
 Id: 5, Name: Red, Owner: 3, Type: horse
 Id: 3, Name: Sneaky, Owner: 5, Type: snake
 Id: 7, Name: Fido, Owner: 7, Type: cat

 New People Data:
 Id: 2, Name: Kim, Age: 27, Notes: I like birds
 Id: 3, Name: Cheryl, Age: 23, Notes: I like horses
 Id: 4, Name: Bob, Age: 27, Notes: I like rabbits
 Id: 6, Name: Pete, Age: 23, Notes: I like cats
 Id: 7, Name: Pat, Age: 36, Notes: I like dogs

 New Pet Data:
 Id: 1, Name: Duke, Owner: 2, Type: dog
 Id: 2, Name: Dragon, Owner: 2, Type: bird
 Id: 4, Name: Red, Owner: 2, Type: bird
 Id: 6, Name: Buster, Owner: 2, Type: dog
 Id: 5, Name: Red, Owner: 3, Type: horse
 Id: 7, Name: Fido, Owner: 7, Type: cat
Answer
Some other things you could try
  • Change the database constraints to delete or Null the child record on delete (a cascading delete).  Delete a person and let the database handle the children.
  • Remove the people who don’t have any pets.

Series sections

Initial Setup
Create records
Retrieve records
Update records
Delete records

Delete (cruD) using Perl and DBD::ORACLE

In this post, we’re going to take a look at the D in CRUD: Delete.

We use the DBD::Oracle driver to delete some data in the database tables, using the connection object created in the Initial Setup section of the first post in this series.

PLEASE REVIEW ALL EXAMPLE CODE AND ONLY RUN IT IF YOU ARE SURE IT WILL NOT CAUSE ANY PROBLEMS WITH YOUR SYSTEM.

Helper Function

My helper function get_all_rows encapsulates a select statement used to verify that the deletes worked. The select functionality is covered in the R part of this series, so I won’t go into the details here.

sub get_all_rows {
 my $label = $_[0];
 my $data_type = $_[1];

 # Query all rows
 my $con = DBI->connect( 'dbi:Oracle:', $connectString, '') ||
 die "Database connection not made: $DBI::errstr";
 $con->{RaiseError} = 1; # set the connection to raise errors

 my $statement = 'select id, name, age, notes from lcs_people order by id';

 if ($data_type eq "pets") {
   $statement = 'select id, name, owner, type from lcs_pets order by owner, id';
 }

 my $sth = $con->prepare($statement);
 $sth->execute;

 #Adding some space around the results to make better screenshots.
 print "\n $label: \n";
 while (my @row = $sth->fetchrow_array){
   print " @row\n";
 }
 print "\n";

 $con->disconnect;
}

Add this function to the top of your file.

Resetting the data

To keep the examples clean and precise, I will reset the data at times.

Create a new file called reset_data.perl with the following code and run it whenever you would like to reset the data. (Notice this version adds people and pet data not included in other sections.)

use strict;
use DBI;
my $connectString=$ENV{'db_connect'};
my $con = DBI->connect( 'dbi:Oracle:', $connectString, '');
$con->{RaiseError} = 1; # set the connection to raise errors

# Delete rows
my $sth = $con->prepare("delete from lcs_pets");
$sth->execute;

# Reset Identity Coulmn
my $sth = $con->prepare("alter table lcs_pets modify id generated BY DEFAULT as identity (START WITH 8)");
$sth->execute;

# Delete rows
my $sth = $con->prepare("delete from lcs_people");
$sth->execute;

# Reset Identity Coulmn
my $sth = $con->prepare("alter table lcs_people modify id generated BY DEFAULT as identity (START WITH 8)");
$sth->execute;

# Insert default rows
my @ids = (1, 2, 3, 4, 5, 6, 7);
my @names = ("Bob", "Kim", "Cheryl", "Bob", "Stacey", "Pete", "Pat");
my @ages = (35, 27, 23, 27, 45, 23, 36);
my @notes = ("I like dogs", "I like birds", "I like horses", "I like rabbits", "I like snakes", "I like cats", "I like dogs");

my $sth = $con->prepare("INSERT INTO lcs_people(id, name, age, notes) VALUES (?, ?, ?, ?)");
my $tuples = $sth->execute_array(
 { ArrayTupleStatus => \my @tuple_status }, \@ids, \@names, \@ages, \@notes,);
if ($tuples) {
 print "Successfully inserted $tuples records\n";
} else {
 print "Insert failed\n";
}

# Insert default rows
my @ids = (1, 2, 3, 4, 5, 6, 7);
my @names = ("Duke", "Dragon", "Sneaky", "Red", "Red", "Buster", "Fido");
my @owners = (1, 2, 5, 2, 3, 1, 7);
my @types = ("dog", "bird", "snake", "bird", "horse", "dog", "cat");

my $sth = $con->prepare("INSERT INTO lcs_pets(id, name, owner, type) VALUES (?, ?, ?, ?)");
my $tuples = $sth->execute_array(
 { ArrayTupleStatus => \my @tuple_status }, \@ids, \@names, \@owners, \@types,);
if ($tuples) {
 print "Successfully inserted $tuples records\n";
} else {
 print "Insert failed\n";
}

$con->disconnect;
Boilerplate template

The template we will be using is:

use strict;
use DBI;
my $connectString=$ENV{'db_connect'};

sub get_all_rows {
 my $label = $_[0];
 my $data_type = $_[1];

 # Query all rows
 my $con = DBI->connect( 'dbi:Oracle:', $connectString, '') ||
 die "Database connection not made: $DBI::errstr";
 $con->{RaiseError} = 1; # set the connection to raise errors

 my $statement = 'select id, name, age, notes from lcs_people order by id';

 if ($data_type eq 'pets') {
   $statement = 'select id, name, owner, type from lcs_pets order by owner, id';
 }

 my $sth = $con->prepare($statement);
 $sth->execute;

 #Adding some space around the results to make better screenshots.
 print "\n $label: \n";
 while (my @row = $sth->fetchrow_array){
   print " @row\n";
 }
 print "\n";

 $con->disconnect;
}

my $con = DBI->connect( 'dbi:Oracle:', $connectString, '') || die "Database connection not made: $DBI::errstr";
$con->{RaiseError} = 1; # set the connection to raise errors

get_all_rows('Original Data', 'pets');

# Your code here

get_all_rows('New Data', 'pets');

For each exercise, replace the “# Your code here” line with your code.

Reset the data

First, let’s run reset_data.perl to set up our data.

Simple delete

We will perform a simple delete that removes a single record from the lcs_people table.  These are the steps performed in the code snippet below.

  • Prepare a SQL DELETE statement, deleting the record with an id of 1.
  • Bind the id value. (See the R part of this series for an explanation of bind variables.)
  • Execute the statement.
my $sth = $con->prepare("delete from lcs_pets where id = :id");
$sth->bind_param( ":id",1);
$sth->execute;

When I run this code in my Perl session, I see:

 Original Data: 
 1 Duke 1 dog
 6 Buster 1 dog
 2 Dragon 2 bird
 4 Red 2 bird
 5 Red 3 horse
 3 Sneaky 5 snake
 7 Fido 7 cat

 New Data: 
 6 Buster 1 dog
 2 Dragon 2 bird
 4 Red 2 bird
 5 Red 3 horse
 3 Sneaky 5 snake
 7 Fido 7 cat

Extra Fun 1

Delete all the birds .

Your results should be:

 Original Data: 
 6 Buster 1 dog
 2 Dragon 2 bird
 4 Red 2 bird
 5 Red 3 horse
 3 Sneaky 5 snake
 7 Fido 7 cat


 New Data: 
 6 Buster 1 dog
 5 Red 3 horse
 3 Sneaky 5 snake
 7 Fido 7 cat
Answer
Reset the data

Now is a good time to run reset_data.perl.

Boilerplate change

Change the boilerplate get_all_rows statements to get people and pet data.

get_all_rows('Original People Data', 'people');
get_all_rows('Original Pet Data', 'pets');

# Your code here

get_all_rows('New People Data', 'people');
get_all_rows('New Pet Data', 'pets');
Deleting records referenced by Foreign Keys

If you are using integrity constraints in your database (of course you are, because then you let the database do some heavy lifting for you), you will sometimes need to change the way you process your changes.

In our design, we have a Foreign Key constraint in lcs_pets that ensures if a pet has an owner, that owner exists.

This is the statement that creates the constraint in the Creating the Database Objects section of the Initial Setup post.

ALTER TABLE LCS_PETS ADD CONSTRAINT FK_LCS_PETS_OWNER FOREIGN KEY ("OWNER") REFERENCES "LCS_PEOPLE" ("ID")
/

If we attempt to delete a record in lcs_people that is referenced in lcs_pets (Person has a pet,) we get an error.

my $sth = $con->prepare("delete from lcs_people where id = :id");
$sth->bind_param( ":id",1);
$sth->execute;

When I run this code in my Perl session, I see:

DBD::Oracle::st execute failed: ORA-02292: integrity constraint (BLAINE.FK_LCS_PETS_OWNER) violated - child record found (DBD ERROR: OCIStmtExecute) [for Statement "delete from lcs_people where id = :id" with ParamValues: :id=1] at delete2.perl line 41.
DBD::Oracle::st execute failed: ORA-02292: integrity constraint (BLAINE.FK_LCS_PETS_OWNER) violated - child record found (DBD ERROR: OCIStmtExecute) [for Statement "delete from lcs_people where id = :id" with ParamValues: :id=1] at delete2.perl line 41.

Before deleting the person you have to handle the pet (watch out for claws and teeth).

There are a few options here, depending on your database design:

  • If: pets are not required to have an owner and you only want to delete the person, not the pets.  Then: you can update the pets and set their owner to null.
  • If: pets are required to have an owner.  Then: you can delete the pets for the owner.

In either of the above scenarios, you can update the pets and set their owner to another person.

Bob is moving out of our area and his new apartment doesn’t allow pets, so he’s giving them to Kim.  Let’s use that last option here.

  • Prepare a SQL UPDATE statement, changing owner to 2 (Kim) for the records with an owner of 1 (Bob).  Updating is covered in the U part of this series.
  • Bind the new and old owner values.
  • Execute the statement.
  • Prepare a SQL DELETE statement, deleting records with an id of 1 (Bob).
  • Bind the id value.
  • Execute the statement.
my $sth = $con->prepare("update lcs_pets set owner = :newOwner where owner = :oldOwner");
$sth->bind_param(":newOwner",2);
$sth->bind_param(":oldOwner",1);
$sth->execute;

my $sth = $con->prepare("delete from lcs_people where id = :id");
$sth->bind_param(":id",1);
$sth->execute;

When I run this code in my Perl session, I see:

 Original People Data: 
 1 Bob 35 I like dogs
 2 Kim 27 I like birds
 3 Cheryl 23 I like horses
 4 Bob 27 I like rabbits
 5 Stacey 45 I like snakes
 6 Pete 23 I like cats
 7 Pat 36 I like dogs


 Original Pet Data: 
 1 Duke 1 dog
 6 Buster 1 dog
 2 Dragon 2 bird
 4 Red 2 bird
 5 Red 3 horse
 3 Sneaky 5 snake
 7 Fido 7 cat


 New People Data: 
 2 Kim 27 I like birds
 3 Cheryl 23 I like horses
 4 Bob 27 I like rabbits
 5 Stacey 45 I like snakes
 6 Pete 23 I like cats
 7 Pat 36 I like dogs


 New Pet Data: 
 1 Duke 2 dog
 2 Dragon 2 bird
 4 Red 2 bird
 6 Buster 2 dog
 5 Red 3 horse
 3 Sneaky 5 snake
 7 Fido 7 cat

When you change data it’s a good idea to verify the number of affected rows.  This is covered in the R part of this series.

Extra Fun 2

Due to a zoning change, snakes are no longer allowed in our area.  Stacey has decided to move and take Sneaky with her.

Let’s fix our data.

Your results should be:

 Original People Data: 
 2 Kim 27 I like birds
 3 Cheryl 23 I like horses
 4 Bob 27 I like rabbits
 5 Stacey 45 I like snakes
 6 Pete 23 I like cats
 7 Pat 36 I like dogs


 Original Pet Data: 
 1 Duke 2 dog
 2 Dragon 2 bird
 4 Red 2 bird
 6 Buster 2 dog
 5 Red 3 horse
 3 Sneaky 5 snake
 7 Fido 7 cat


 New People Data: 
 2 Kim 27 I like birds
 3 Cheryl 23 I like horses
 4 Bob 27 I like rabbits
 6 Pete 23 I like cats
 7 Pat 36 I like dogs


 New Pet Data: 
 1 Duke 2 dog
 2 Dragon 2 bird
 4 Red 2 bird
 6 Buster 2 dog
 5 Red 3 horse
 7 Fido 7 cat
Answer
Some other things you could try
  • Change the database constraints to delete or Null the child record on delete (a cascading delete).  Delete a person and let the database handle the children.
  • Remove the people who don’t have any pets.

Series sections

Initial Setup
Create records
Retrieve records
Update records
Delete records

Update (crUd) using Ruby-OCI8

In this post, we’re going to take a look at the U in CRUD: Update.

We use the ruby-oci8 driver to update some data in the database tables, using the connection object created in the Initial Setup section of the first post in this series.

PLEASE REVIEW ALL EXAMPLE CODE AND ONLY RUN IT IF YOU ARE SURE IT WILL NOT CAUSE ANY PROBLEMS WITH YOUR SYSTEM.

Helper Function

My helper function get_all_rows() encapsulates a select statement used to verify that the updates worked. The select functionality is covered in the R part of this series, so I won’t go into the details here.

def get_all_rows (label, data_type = 'people')
 connectString = ENV['db_connect']
 con = OCI8.new(connectString)

 # Query all rows
 statement = 'select id, name, age, notes from lcs_people order by id';

 if data_type == 'pets'
 statement = 'select id, name, owner, type from lcs_pets order by owner, id'
 end

 cursor = con.parse(statement)
 cursor.exec
 printf " %s:\n", label
 cursor.fetch() {|row|
   if data_type == 'people'
     printf " Id: %d, Name: %s, Age: %d, Notes: %s\n", row[0], row[1], row[2], row[3]
   else
     printf " Id: %d, Name: %s, Owner: %d, Type: %s\n", row[0], row[1], row[2], row[3]
   end
 }
 printf "\n"
end

Add this function to the top of your file.

Resetting the data

To keep the examples clean and precise, I will reset the data at times.

Create a new file called reset_data.rb with the following code and then run it whenever you would like to reset the data. (Notice this version adds pet data not included in other sections.)

# Query all rows
require 'oci8'
connectString = ENV['db_connect']
con = OCI8.new(connectString)

# Delete rows
cursor = con.parse("delete from lcs_pets")
cursor.exec

# Reset Identity Coulmn
cursor = con.parse("alter table lcs_pets modify id generated BY DEFAULT as identity (START WITH 8)")
cursor.exec

# Delete rows
cursor = con.parse("delete from lcs_people")
cursor.exec

# Reset Identity Coulmn
cursor = con.parse("alter table lcs_people modify id generated BY DEFAULT as identity (START WITH 3)")
cursor.exec

# Insert default people rows
cursor = con.parse("INSERT INTO lcs_people(id, name, age, notes) VALUES (:id, :name, :age, :notes)")
cursor.max_array_size = 2
cursor.bind_param_array(:id, [1, 2])
cursor.bind_param_array(:name, ["Bob", "Kim"])
cursor.bind_param_array(:age, [35, 27])
cursor.bind_param_array(:notes, ["I like dogs", "I like birds"])
people_row_count = cursor.exec_array
printf " %d people rows inserted\n", people_row_count

# Insert default pet rows
cursor = con.parse("INSERT INTO lcs_pets(id, name, owner, type) VALUES (:id, :name, :owner, :type)")
cursor.max_array_size = 7
cursor.bind_param_array(:id, [1, 2, 3, 4, 5, 6, 7])
cursor.bind_param_array(:name, ["Duke", "Pepe", "Princess", "Polly", "Rollo", "Buster", "Fido"])
cursor.bind_param_array(:owner, [1, 2, 1, 1, 1, 1, 1])
cursor.bind_param_array(:type, ["dog", "bird", "snake", "bird", "horse", "dog", "cat"])
pet_row_count = cursor.exec_array
printf " %d pet rows inserted\n", pet_row_count

con.commit
Boilerplate template

The template we will be using is:

require 'oci8'
connectString = ENV['db_connect']

def get_all_rows (label, data_type = 'people')
 connectString = ENV['db_connect']
 con = OCI8.new(connectString)

 # Query all rows
 statement = 'select id, name, age, notes from lcs_people order by id';

 if data_type == 'pets'
   statement = 'select id, name, owner, type from lcs_pets order by owner, id'
 end

 cursor = con.parse(statement)
 cursor.exec
 printf " %s:\n", label
 cursor.fetch() {|row|
   if data_type == 'people'
     printf " Id: %d, Name: %s, Age: %d, Notes: %s\n", row[0], row[1], row[2], row[3]
   else
     printf " Id: %d, Name: %s, Owner: %d, Type: %s\n", row[0], row[1], row[2], row[3]
   end
 }
 printf "\n"
end

con = OCI8.new(connectString)

get_all_rows('Original Data')

# Your code here

get_all_rows('New Data')

For each exercise, replace the “# Your code here” line with your code.

Simple update

We will perform a simple update that modifies a single record in the lcs_people table.  These are the steps performed in the code snippet below.

  • Prepare a SQL UPDATE statement, changing age to 31 for the record with an id of 1.
  • Parse the statement to create a cursor.
  • Bind the age and id values.  (See the R part of this series for an explanation of bind variables.)
  • Execute the statement.
  • Commit the transaction.
statement = "update lcs_people set age = :age where id = :id"
cursor = con.parse(statement)
cursor.bind_param(:age,31)
cursor.bind_param(:id,1)
cursor.exec
con.commit

When I run this code in my Ruby session, I see:

 Example: ruby update1.rb 
 Original Data:
 Id: 1, Name: Bob, Age: 35, Notes: I like dogs
 Id: 2, Name: Kim, Age: 27, Notes: I like birds

 New Data:
 Id: 1, Name: Bob, Age: 31, Notes: I like dogs
 Id: 2, Name: Kim, Age: 27, Notes: I like birds
Extra Fun 1

Update Bob’s notes to ‘I like cats’ .

Your results should be:

 Original Data:
 Id: 1, Name: Bob, Age: 31, Notes: I like dogs
 Id: 2, Name: Kim, Age: 27, Notes: I like birds

 New Data:
 Id: 1, Name: Bob, Age: 31, Notes: I like cats
 Id: 2, Name: Kim, Age: 27, Notes: I like birds
Answer
Reset the data

Now is a good time to run reset_data.rb.

Boilerplate change

Change the boilerplate get_all_rows statements to get pet data.

get_all_rows('Original Data', 'pets');

# Your code here

get_all_rows('New Data', 'pets');
Make sure your where clause is specific

In the above example, notice that we used the id column in our where clause.  For our data set, id is the primary key.  You do not always have to use a primary key, but you should make sure you only update the rows you intend to.

Next, let’s look at updating multiple rows.   We’ll have Bob give his dog Duke to Kim.

  • Prepare a SQL UPDATE statement, changing owner to 2 for the record with an owner of 1 and a type of ‘dog’.
  • Parse the statement to create a cursor.
  • Bind the newOwner, oldOwner and type values.
  • Execute the statement.
  • Commit the transaction.
statement = "update lcs_pets set owner = :newOwner where owner = :oldOwner and type = :type"
cursor = con.parse(statement)
cursor.bind_param(:newOwner,2)
cursor.bind_param(:oldOwner,1)
cursor.bind_param(:type,"dog")
cursor.exec
con.commit

When I run this code in my Ruby session, I see:

 Original Data:
 Id: 1, Name: Duke, Owner: 1, Type: dog
 Id: 3, Name: Princess, Owner: 1, Type: snake
 Id: 4, Name: Polly, Owner: 1, Type: bird
 Id: 5, Name: Rollo, Owner: 1, Type: horse
 Id: 6, Name: Buster, Owner: 1, Type: dog
 Id: 7, Name: Fido, Owner: 1, Type: cat
 Id: 2, Name: Pepe, Owner: 2, Type: bird

 New Data:
 Id: 3, Name: Princess, Owner: 1, Type: snake
 Id: 4, Name: Polly, Owner: 1, Type: bird
 Id: 5, Name: Rollo, Owner: 1, Type: horse
 Id: 7, Name: Fido, Owner: 1, Type: cat
 Id: 1, Name: Duke, Owner: 2, Type: dog
 Id: 2, Name: Pepe, Owner: 2, Type: bird
 Id: 6, Name: Buster, Owner: 2, Type: dog

In our example we only used owner and type, assuming that Bob only had one dog, Duke, as it is in our original data.  With the new reset data function, we added a second dog, Buster.  This example is intended to demonstrate what may happen when multiple users are working with the same data set.

In our data, the only unique identifier for lcs_pets is id.  Bob may have two dogs, or even two dogs named Duke.  Make sure if you intend to change a specific row you use a unique identifier.

It also helps to…

Verify the number of affected rows

Now let’s give Buster back to Bob.  This time we will use the unique id column and we will print out the number of rows affected using the return value from cursor.exe.

  • Prepare a SQL UPDATE statement.
  • Parse the statement to create a cursor.
  • Bind the newOwner to 1 and id to 6.
  • Execute the statement returning the number of changed rows.
  • Commit the transaction.
  • Print the number of changed rows.
statement = "update lcs_pets set owner = :newOwner where id = :id"
cursor = con.parse(statement)
cursor.bind_param(:newOwner,2)
cursor.bind_param(:id,6)
changed = cursor.exec
con.commit

printf "Number of rows updated: %d\n\n", changed

When I run this code in my Ruby session, I see:

 Original Data:
 Id: 3, Name: Princess, Owner: 1, Type: snake
 Id: 4, Name: Polly, Owner: 1, Type: bird
 Id: 5, Name: Rollo, Owner: 1, Type: horse
 Id: 7, Name: Fido, Owner: 1, Type: cat
 Id: 1, Name: Duke, Owner: 2, Type: dog
 Id: 2, Name: Pepe, Owner: 2, Type: bird
 Id: 6, Name: Buster, Owner: 2, Type: dog

Number of rows updated: 1

 New Data:
 Id: 3, Name: Princess, Owner: 1, Type: snake
 Id: 4, Name: Polly, Owner: 1, Type: bird
 Id: 5, Name: Rollo, Owner: 1, Type: horse
 Id: 7, Name: Fido, Owner: 1, Type: cat
 Id: 1, Name: Duke, Owner: 2, Type: dog
 Id: 2, Name: Pepe, Owner: 2, Type: bird
 Id: 6, Name: Buster, Owner: 2, Type: dog

cursor.exe will return the number of rows affected for insert, update and delete statements and for a select statement, it returns the number of the select-list.

Extra Fun 2

Give all birds to Kim that she doesn’t already have and print the number of affected rows .

Your results should be:

 Original Data:
 Id: 3, Name: Princess, Owner: 1, Type: snake
 Id: 4, Name: Polly, Owner: 1, Type: bird
 Id: 5, Name: Rollo, Owner: 1, Type: horse
 Id: 7, Name: Fido, Owner: 1, Type: cat
 Id: 1, Name: Duke, Owner: 2, Type: dog
 Id: 2, Name: Pepe, Owner: 2, Type: bird
 Id: 6, Name: Buster, Owner: 2, Type: dog

Number of rows updated: 1

 New Data:
 Id: 3, Name: Princess, Owner: 1, Type: snake
 Id: 5, Name: Rollo, Owner: 1, Type: horse
 Id: 7, Name: Fido, Owner: 1, Type: cat
 Id: 1, Name: Duke, Owner: 2, Type: dog
 Id: 2, Name: Pepe, Owner: 2, Type: bird
 Id: 4, Name: Polly, Owner: 2, Type: bird
 Id: 6, Name: Buster, Owner: 2, Type: dog
Answer
Some other things you could try
  • Change multiple column values
  • Perform an update that changes all rows, if the row count is greater than 2, rollback the change

Series sections

Initial Setup
Create records
Retrieve records
Update records
Delete records

Update (crUd) using Perl and DBD::ORACLE

In this post, we’re going to take a look at the U in CRUD: Update.

We use the DBD::Oracle driver to update some data in the database tables, using the connection object created in the Initial Setup section of the first post in this series.

PLEASE REVIEW ALL EXAMPLE CODE AND ONLY RUN IT IF YOU ARE SURE IT WILL NOT CAUSE ANY PROBLEMS WITH YOUR SYSTEM.

Helper Function

My helper function get_all_rows() encapsulates a select statement used to verify that the updates worked. The select functionality is covered in the R part of this series, so I won’t go into the details here.

sub get_all_rows {
 my $label = $_[0];
 my $data_type = $_[1];

 # Query all rows
 my $con = DBI->connect( 'dbi:Oracle:', $connectString, '') ||
 die "Database connection not made: $DBI::errstr";
 $con->{RaiseError} = 1; # set the connection to raise errors

 my $statement = 'select id, name, age, notes from lcs_people order by id';

 if ($data_type eq "pets") {
   $statement = 'select id, name, owner, type from lcs_pets order by owner, id';
 }

 my $sth = $con->prepare($statement);
 $sth->execute;

 #Adding some space around the results to make better screenshots.
 print "\n $label: \n";
 while (my @row = $sth->fetchrow_array){
 print " @row\n";
 }
 print "\n";

 $con->disconnect;
}

Add this function to the top of your file.

Resetting the data

To keep the examples clean and precise, I will reset the data at times.

Create a new file called reset_data.perl with the following code and then run it whenever you would like to reset the data. (Notice this version adds pet data not included in other sections.)

use strict;
use DBI;
my $connectString=$ENV{'db_connect'};
my $con = DBI->connect( 'dbi:Oracle:', $connectString, '');
$con->{RaiseError} = 1; # set the connection to raise errors

# Delete rows
my $sth = $con->prepare("delete from lcs_pets");
$sth->execute;

# Reset Identity Coulmn
my $sth = $con->prepare("alter table lcs_pets modify id generated BY DEFAULT as identity (START WITH 8)");
$sth->execute;

# Delete rows
my $sth = $con->prepare("delete from lcs_people");
$sth->execute;

# Reset Identity Coulmn
my $sth = $con->prepare("alter table lcs_people modify id generated BY DEFAULT as identity (START WITH 3)");
$sth->execute;

# Insert default rows
my @ids = (1, 2);
my @names = ("Bob", "Kim");
my @ages = (35, 27);
my @notes = ("I like dogs", "I like birds");

my $sth = $con->prepare("INSERT INTO lcs_people(id, name, age, notes) VALUES (?, ?, ?, ?)");
my $tuples = $sth->execute_array(
 { ArrayTupleStatus => \my @tuple_status }, \@ids, \@names, \@ages, \@notes,);
if ($tuples) {
 print "Successfully inserted $tuples records\n";
} else {
 print "Insert failed\n";
}

# Insert default rows
my @ids = (1, 2, 3, 4, 5, 6, 7);
my @names = ("Duke", "Pepe", "Princess", "Polly", "Rollo", "Buster", "Fido");
my @owners = (1, 2, 1, 1, 1, 1, 1);
my @types = ("dog", "bird", "snake", "bird", "horse", "dog", "cat");

my $sth = $con->prepare("INSERT INTO lcs_pets(id, name, owner, type) VALUES (?, ?, ?, ?)");
my $tuples = $sth->execute_array(
 { ArrayTupleStatus => \my @tuple_status }, \@ids, \@names, \@owners, \@types,);
if ($tuples) {
 print "Successfully inserted $tuples records\n";
} else {
 print "Insert failed\n";
}

$con->disconnect;
Boilerplate template

The template we will be using is:

use strict;
use DBI;
my $connectString=$ENV{'db_connect'};

sub get_all_rows {
 my $label = $_[0];
 my $data_type = $_[1];

 # Query all rows
 my $con = DBI->connect( 'dbi:Oracle:', $connectString, '') ||
 die "Database connection not made: $DBI::errstr";
 $con->{RaiseError} = 1; # set the connection to raise errors

 my $statement = 'select id, name, age, notes from lcs_people order by id';

 if ($data_type eq 'pets') {
 $statement = 'select id, name, owner, type from lcs_pets order by owner, id';
 }

 my $sth = $con->prepare($statement);
 $sth->execute;

 #Adding some space around the results to make better screenshots.
 print "\n $label: \n";
 while (my @row = $sth->fetchrow_array){
 print " @row\n";
 }
 print "\n";

 $con->disconnect;
}

my $con = DBI->connect( 'dbi:Oracle:', $connectString, '') || die "Database connection not made: $DBI::errstr";
$con->{RaiseError} = 1; # set the connection to raise errors

get_all_rows('Original Data');

# Your code here

get_all_rows('New Data')

For each exercise, replace the “# Your code here” line with your code.

Simple update

We will perform a simple update that modifies a single record in the lcs_people table.  These are the steps performed in the code snippet below.

  • Prepare a SQL UPDATE statement, changing age to 31 for the record with an id of 1.
  • Bind the age and id values.  (See the R part of this series for an explanation of bind variables.)
  • Execute the statement.
my $sth = $con->prepare("update lcs_people set age = :age where id = :id");
$sth->bind_param( ":age",31);
$sth->bind_param( ":id",1);
$sth->execute;

When I run this code in my Perl session, I see:

 Original Data: 
 1 Bob 35 I like dogs
 2 Kim 27 I like birds

 New Data: 
 1 Bob 31 I like dogs
 2 Kim 27 I like birds
Extra Fun 1

Update Bob’s notes to ‘I like cats’ .

Your results should be:

 Original Data: 
 1 Bob 31 I like dogs
 2 Kim 27 I like birds

 New Data: 
 1 Bob 31 I like cats
 2 Kim 27 I like birds
Answer
Reset the data

Now is a good time to run reset_data.perl.

Boilerplate change

Change the boilerplate get_all_rows statements to get pet data.

get_all_rows('Original Data', 'pets');

# Your code here

get_all_rows('New Data', 'pets');
Make sure your where clause is specific

In the above example, notice that we used the id column in our where clause.  For our data set, id is the primary key.  You do not always have to use a primary key, but you should make sure you only update the rows you intend to.

Next, let’s look at updating multiple rows.   We’ll have Bob give his dog Duke to Kim.

  • Prepare a SQL UPDATE statement, changing owner to 2 for the record with an owner of 1 and a type of ‘dog’.
  • Bind the newOwner, oldOwner and type values.
  • Execute the statement.
my $sth = $con->prepare("update lcs_pets set owner = :newOwner where owner = :oldOwner and type = :type");
$sth->bind_param( ":newOwner",2);
$sth->bind_param( ":oldOwner",1);
$sth->bind_param( ":type","dog");
$sth->execute;

When I run this code in my Perl session, I see:

 Original Data: 
 1 Duke 1 dog
 3 Princess 1 snake
 4 Polly 1 bird
 5 Rollo 1 horse
 6 Buster 1 dog
 7 Fido 1 cat
 2 Pepe 2 bird


 New Data: 
 3 Princess 1 snake
 4 Polly 1 bird
 5 Rollo 1 horse
 7 Fido 1 cat
 1 Duke 2 dog
 2 Pepe 2 bird
 6 Buster 2 dog

In our example we only used owner and type, assuming that Bob only had one dog, Duke, as it is in our original data.  With the new reset data function, we added a second dog, Buster.  This example is intended to demonstrate what may happen when multiple users are working with the same data set.

In our data, the only unique identifier for lcs_pets is id.  Bob may have two dogs, or even two dogs named Duke.  Make sure if you intend to change a specific row you use a unique identifier.

It also helps to…

Verify the number of affected rows

Now let’s give Buster back to Bob.  This time we will use the unique id column and we will print out the number of rows affected using $sth->rows.

  • Prepare a SQL UPDATE statement.
  • Bind the newOwner to 1 and id to 6.
  • Execute the statement.
  • Get the number of changed rows.
  • Print the number of changed rows.
my $sth = $con->prepare("update lcs_pets set owner = :newOwner where id = :id");
$sth->bind_param( ":newOwner",1);
$sth->bind_param( ":id",6);
$sth->execute;

my $changed = $sth->rows;

print "Number of rows updated: $changed\n";

When I run this code in my Perl session, I see:

 Original Data: 
 3 Princess 1 snake
 4 Polly 1 bird
 5 Rollo 1 horse
 7 Fido 1 cat
 1 Duke 2 dog
 2 Pepe 2 bird
 6 Buster 2 dog

Number of rows updated: 1

 New Data: 
 3 Princess 1 snake
 4 Polly 1 bird
 5 Rollo 1 horse
 6 Buster 1 dog
 7 Fido 1 cat
 1 Duke 2 dog
 2 Pepe 2 bird

$sth->rows will show you the number of rows affected for insert, update and delete statements and -1 for a select statement.

Extra Fun 2

Give all birds to Kim that she doesn’t already have and print the number of affected rows .

Your results should be:

 Original Data: 
 3 Princess 1 snake
 4 Polly 1 bird
 5 Rollo 1 horse
 6 Buster 1 dog
 7 Fido 1 cat
 1 Duke 2 dog
 2 Pepe 2 bird

Number of rows updated: 1

 New Data: 
 3 Princess 1 snake
 5 Rollo 1 horse
 6 Buster 1 dog
 7 Fido 1 cat
 1 Duke 2 dog
 2 Pepe 2 bird
 4 Polly 2 bird
Answer
Some other things you could try
  • Change multiple column values
  • Perform an update that changes all rows, if the row count is greater than 2, rollback the change

Series sections

Initial Setup
Create records
Retrieve records
Update records
Delete records

Insert (Crud) using Ruby-OCI8

In this post, we’re going to take a look at the C in CRUD: Create.

We will be using the ruby-oci8 driver to create some data in the database tables, using the connection object created in the Initial Setup section of the first post in this series.

PLEASE REVIEW ALL EXAMPLE CODE AND ONLY RUN IT IF YOU ARE SURE IT WILL NOT CAUSE ANY PROBLEMS WITH YOUR SYSTEM.

Helper Function

I will be using a helper function get_all_rows(). This is a select statement used to verify that the inserts worked. The select functionality is covered in the R part of this series, so I won’t go into the details here.

def get_all_rows (label)
 con = OCI8.new(connectString)

 # Query all rows
 statement = 'select id, name, age, notes from lcs_people order by id'
 cursor = con.parse(statement)
 cursor.exec
 cursor.fetch() {|row|
 printf "Id: %d, Name: %s, Age: %d, Notes: %s\n", row[0], row[1], row[2], row[3]
 }
 printf "\n"
end

Add this function to the top of your file.

Resetting the data

To keep the examples clean and precise, I will reset the data at times.

Create a new file called reset_data.rb with the following code and then run it whenever you would like to reset the data.

# Query all rows
require 'oci8'
connectString = ENV['db_connect']
con = OCI8.new(connectString)

# Delete rows
cursor = con.parse("delete from lcs_pets")
cursor.exec

# Reset Identity Coulmn
cursor = con.parse("alter table lcs_pets modify id generated BY DEFAULT as identity (START WITH 3)")
cursor.exec

# Delete rows
cursor = con.parse("delete from lcs_people")
cursor.exec

# Reset Identity Coulmn
cursor = con.parse("alter table lcs_people modify id generated BY DEFAULT as identity (START WITH 3)")
cursor.exec

# Insert default people rows
cursor = con.parse("INSERT INTO lcs_people(id, name, age, notes) VALUES (:id, :name, :age, :notes)")
cursor.max_array_size = 2
cursor.bind_param_array(:id, [1, 2])
cursor.bind_param_array(:name, ["Bob", "Kim"])
cursor.bind_param_array(:age, [35, 27])
cursor.bind_param_array(:notes, ["I like dogs", "I like birds"])
people_row_count = cursor.exec_array
printf " %d people rows inserted\n", people_row_count

# Insert default pet rows
cursor = con.parse("INSERT INTO lcs_pets(id, name, owner, type) VALUES (:id, :name, :owner, :type)")
cursor.max_array_size = 2
cursor.bind_param_array(:id, [1, 2])
cursor.bind_param_array(:name, ["Duke", "Pepe"])
cursor.bind_param_array(:owner, [1, 2])
cursor.bind_param_array(:type, ["dog", "bird"])
pet_row_count = cursor.exec_array
printf " %d pet rows inserted\n", pet_row_count

con.commit
Boilerplate template

The template we will be using is:

# Query all rows
require 'oci8'
connectString = ENV['db_connect']

def get_all_rows (label)
 connectString = ENV['db_connect']
 con = OCI8.new(connectString)

 # Query all rows
 statement = 'select id, name, age, notes from lcs_people order by id'
 cursor = con.parse(statement)
 cursor.exec
 printf " %s:\n", label
 cursor.fetch() {|row|
 printf "  Id: %d, Name: %s, Age: %d, Notes: %s\n", row[0], row[1], row[2], row[3]
 }
 printf "\n"
end

con = OCI8.new(connectString)

get_all_rows('Original Data')

# Your code here

get_all_rows('New Data')

For each exercise, replace the “# Your code here” line with your code.

Simple insert

We will perform a simple insert that adds a single record into the lcs_people table.  These are the steps performed in the code snippet below.

  • Prepare a SQL INSERT statement, specifying the table and columns to insert the data.
  • Parse the statement to create a cursor.
  • Bind the three parameters to their values.  (See the R part of this series for an explanation of bind variables)
  • Execute the statement.
  • Commit the transaction.
statement = "insert into lcs_people(name, age, notes) values (:name, :age, :notes)"
cursor = con.parse(statement)
cursor.bind_param(:name,"Sandy")
cursor.bind_param(:age,31)
cursor.bind_param(:notes,"I like horses")
cursor.exec
con.commit

When I run this code in my Ruby session, I see:

Original Data:
 Id: 1, Name: Bob, Age: 35, Notes: I like dogs
 Id: 2, Name: Kim, Age: 27, Notes: I like birds

New Data:
 Id: 1, Name: Bob, Age: 35, Notes: I like dogs
 Id: 2, Name: Kim, Age: 27, Notes: I like birds
 Id: 3, Name: Sandy, Age: 31, Notes: I like horses
What is a transaction?

You’ll notice in the bullet points above, I said to commit the transaction.

When you execute Data Manipulation Language or DML statements, such as the insert I use in this post, those changes are only visible to your current connection or session.

Those changes will not be visible to other sessions (even another session connected to the same schema in which the changes were made) until you commit your changes. That step makes it “permanent” in the database, and available for everyone else to see (and possibly change in a future transaction).

Extra Fun 1 & 2

1.  Insert more than 1 row .

Using data for ‘Rob’, 37, ‘I like snakes’ and ‘Cheryl’, 41, ‘I like monkeys’ Your results should be:

Original Data:
 Id: 1, Name: Bob, Age: 35, Notes: I like dogs
 Id: 2, Name: Kim, Age: 27, Notes: I like birds
 Id: 3, Name: Sandy, Age: 31, Notes: I like horses

New Data:
 Id: 1, Name: Bob, Age: 35, Notes: I like dogs
 Id: 2, Name: Kim, Age: 27, Notes: I like birds
 Id: 3, Name: Sandy, Age: 31, Notes: I like horses
 Id: 4, Name: Rob, Age: 37, Notes: I like snakes
 Id: 5, Name: Cheryl, Age: 41, Notes: I like monkeys
 5 Cheryl 41 I like monkeys
Answer

2.  Verify that a second connection cannot see your changes till after the commit.

Using data for ‘Suzy’, 31, ‘I like rabbits’ and assuming that you did the previous exercise your results should be:

Original Data:
 Id: 1, Name: Bob, Age: 35, Notes: I like dogs
 Id: 2, Name: Kim, Age: 27, Notes: I like birds
 Id: 3, Name: Sandy, Age: 31, Notes: I like horses
 Id: 4, Name: Rob, Age: 37, Notes: I like snakes
 Id: 5, Name: Cheryl, Age: 41, Notes: I like monkeys

New connection after insert:
 Id: 1, Name: Bob, Age: 35, Notes: I like dogs
 Id: 2, Name: Kim, Age: 27, Notes: I like birds
 Id: 3, Name: Sandy, Age: 31, Notes: I like horses
 Id: 4, Name: Rob, Age: 37, Notes: I like snakes
 Id: 5, Name: Cheryl, Age: 41, Notes: I like monkeys

Same connection:
 Id: 1, Name: Bob, Age: 35, Notes: I like dogs
 Id: 2, Name: Kim, Age: 27, Notes: I like birds
 Id: 3, Name: Sandy, Age: 31, Notes: I like horses
 Id: 4, Name: Rob, Age: 37, Notes: I like snakes
 Id: 5, Name: Cheryl, Age: 41, Notes: I like monkeys
 Id: 6, Name: Suzy, Age: 31, Notes: I like rabbits

New connection after commit:
 Id: 1, Name: Bob, Age: 35, Notes: I like dogs
 Id: 2, Name: Kim, Age: 27, Notes: I like birds
 Id: 3, Name: Sandy, Age: 31, Notes: I like horses
 Id: 4, Name: Rob, Age: 37, Notes: I like snakes
 Id: 5, Name: Cheryl, Age: 41, Notes: I like monkeys
 Id: 6, Name: Suzy, Age: 31, Notes: I like rabbits

New Data:
 Id: 1, Name: Bob, Age: 35, Notes: I like dogs
 Id: 2, Name: Kim, Age: 27, Notes: I like birds
 Id: 3, Name: Sandy, Age: 31, Notes: I like horses
 Id: 4, Name: Rob, Age: 37, Notes: I like snakes
 Id: 5, Name: Cheryl, Age: 41, Notes: I like monkeys
 Id: 6, Name: Suzy, Age: 31, Notes: I like rabbits

Notice that after the insert, the connection that made the insert can see Suzy but the second connection can’t.

After the commit, both connections see Suzy.

Answer
Reset the data

Now is a good time to run reset_data.rb.

Using Identity Columns

You may have noticed that the id column is not passed in, but is automatically set sequentially.  Prior to Oracle Database 12c, this was accomplished using a sequence and a trigger.

In 12c, this can be accomplished by using an Identity Column.

 CREATE TABLE lcs_people (
 id NUMBER GENERATED BY DEFAULT AS identity,
 ....
 You can find more information on identity columns here(pdf).
Returning data after an insert
 Sometimes we need to perform additional operations after an insert using data generated by the database, such as the identity column above.  For example, let’s add a person and a pet for them.

We could run an insert then select the value back using the name.  But if the name is not unique we’ll have a problem.  This is where the RETURNING clause is helpful.

We will perform an insert that adds a single record into the lcs_people table. Then using the returned id we will add a pet.  These are the steps performed in the code snippet below.

  • Prepare a SQL INSERT statement, specifying the table and columns to insert the people data.
  • Bind the three parameters to their values.
  • Bind the id parameters defining it as a Fixnum type.
  • Execute the statement.
  • Store the returned id in new_id.
  • Prepare a SQL INSERT statement, specifying the table and columns to insert the pet data.
  • Bind the owner parameter to the new_id value, name and type to “Big Red” and “horse”.
  • Execute the statement.
  • Commit both transactions.
  • Print the new_id value.
  • Prepare a SQL statement.
  • Bind the owner parameter to the new_id value.
  • Execute the statement.
  • Print the results with a little decoration text.
statement = "insert into lcs_people(name, age, notes) values (:name, :age, :notes) returning id into :id"
cursor = con.parse(statement)
cursor.bind_param(:name,"Sandy")
cursor.bind_param(:age,31)
cursor.bind_param(:notes,"I like horses")
cursor.bind_param(:id, Fixnum)
cursor.exec

new_id = cursor[:id]

statement = "insert into lcs_pets (name, owner, type) values (:name, :owner, :type)"
cursor = con.parse(statement)
cursor.bind_param(:name,"Big Red")
cursor.bind_param(:owner,new_id)
cursor.bind_param(:type,"horse")
cursor.exec

con.commit

printf " Our new value is: %d\n", new_id

 statement = 'select name, owner, type from lcs_pets where owner = :owner'
 cursor = con.parse(statement)
 cursor.bind_param(:owner, new_id)
 cursor.exec
 printf "\n Sandy\'s pets:\n"
 cursor.fetch() {|row|
 printf " Name: %s, Owner: %d, Type: %s\n", row[0], row[1], row[2]
 }
 printf "\n"

When I run this code in my Ruby session, I see:

Original Data:
 Id: 1, Name: Bob, Age: 35, Notes: I like dogs
 Id: 2, Name: Kim, Age: 27, Notes: I like birds

Our new value is: 3

Sandy's pets:
 Name: Big Red, Owner: 3, Type: horse

New Data:
 Id: 1, Name: Bob, Age: 35, Notes: I like dogs
 Id: 2, Name: Kim, Age: 27, Notes: I like birds
 Id: 3, Name: Sandy, Age: 31, Notes: I like horses

Notice the new value, the owner in Sandy’s pets and Sandy’s id in the New Data are all 3 .

Extra Fun 3

3.  Insert Sandy again but return her id and name.

Your results should be:

Original Data:
 Id: 1, Name: Bob, Age: 35, Notes: I like dogs
 Id: 2, Name: Kim, Age: 27, Notes: I like birds
 Id: 3, Name: Sandy, Age: 31, Notes: I like horses

Our new id is: 4 name: Sandy

New Data:
 Id: 1, Name: Bob, Age: 35, Notes: I like dogs
 Id: 2, Name: Kim, Age: 27, Notes: I like birds
 Id: 3, Name: Sandy, Age: 31, Notes: I like horses
 Id: 4, Name: Sandy, Age: 31, Notes: I like horses

Notice that (3, ‘Sandy’..) is still there along with our new (4, ‘Sandy’..) but the returned id is 4.  It should return the new id each time you run it.

Answer
 Reset the data

Now is a good time to run reset_data.rb.

Insert more than 1 row

As mentioned above, when you want to insert multiple rows, running multiple insert statements is inefficient and makes multiple trips to the database so instead, we will use exec_array.  When your database is capable of bulk processing like Oracle is, the driver will create a much more efficient bulk transaction.

We will perform an insert that adds two records into the lcs_people table.  These are the steps performed in the code snippet below.

  • Prepare a SQL INSERT statement, specifying the table and columns to insert the people data.
  • We need to let the driver know how many records to expect by setting the max_array_size.
  • This time, we use bind_param_array to bind an array with the data for that column to the bind variable for each column.
  • Use exec_array to execute the  statement.  This returns the number of rows inserted which we’ll store in people_row_count.
  • Commit the transaction.
  • Print out the number of records inserted.
cursor = con.parse("INSERT INTO lcs_people(name, age, notes) VALUES (:name, :age, :notes)")
cursor.max_array_size = 2
cursor.bind_param_array(:name, ["Sandy", "Suzy"])
cursor.bind_param_array(:age, [31, 29])
cursor.bind_param_array(:notes, ["I like horses", "I like rabbits"])
people_row_count = cursor.exec_array
con.commit
printf " Successfully inserted %d records\n\n", people_row_count

When I run this code in my Ruby session, I see:

Original Data:
 Id: 1, Name: Bob, Age: 35, Notes: I like dogs
 Id: 2, Name: Kim, Age: 27, Notes: I like birds

Successfully inserted 2 records

New Data:
 Id: 1, Name: Bob, Age: 35, Notes: I like dogs
 Id: 2, Name: Kim, Age: 27, Notes: I like birds
 Id: 3, Name: Sandy, Age: 31, Notes: I like horses
 Id: 4, Name: Suzy, Age: 29, Notes: I like rabbits
Some things you could try
  • Loop through an array of people and insert each one returning its id.  Using that id add multiple pets with exec_array.
  • Create a large array of people.  Time the difference between looping through single inserts and using exec_array.

Series sections

Initial Setup
Create records
Retrieve records
Update records
Delete records

Insert (Crud) using Perl and DBD::ORACLE

In this post, we’re going to take a look at the C in CRUD: Create.

We will be using the DBD::Oracle driver to create some data in the database tables, using the connection object created in the Initial Setup section of the first post in this series.

PLEASE REVIEW ALL EXAMPLE CODE AND ONLY RUN IT IF YOU ARE SURE IT WILL NOT CAUSE ANY PROBLEMS WITH YOUR SYSTEM.

Helper Function

I will be using a helper function get_all_rows(). This is a select statement used to verify that the inserts worked. The select functionality is covered in the R part of this series, so I won’t go into the details here.

sub get_all_rows {
 my $label = $_[0];
 # Query all rows
 my $con = DBI->connect( 'dbi:Oracle:', $connectString, '') || 
    die "Database connection not made: $DBI::errstr";
 $con->{RaiseError} = 1; # set the connection to raise errors
 my $sth = $con->prepare("select id, name, age, notes from lcs_people order by id");
 $sth->execute;

 #Adding some space around the results to make better screenshots.
 print "\n $label: \n";
 while (my @row = $sth->fetchrow_array){
   print " @row\n";
 }
 print "\n";

 $con->disconnect;
}

Add this function to the top of your file.

Resetting the data

To keep the examples clean and precise, I will reset the data at times.

Create a new file called reset_data.perl with the following code and then run it whenever you would like to reset the data.

use strict;
use DBI;
my $connectString=$ENV{'db_connect'};
my $con = DBI->connect( 'dbi:Oracle:', $connectString, '');
$con->{RaiseError} = 1; # set the connection to raise errors

# Delete rows
my $sth = $con->prepare("delete from lcs_pets");
$sth->execute;

# Reset Identity Coulmn
my $sth = $con->prepare("alter table lcs_pets modify id generated BY DEFAULT as identity (START WITH 3)");
$sth->execute;

# Delete rows
my $sth = $con->prepare("delete from lcs_people");
$sth->execute;

# Reset Identity Coulmn
my $sth = $con->prepare("alter table lcs_people modify id generated BY DEFAULT as identity (START WITH 3)");
$sth->execute;

# Insert default rows
my @ids = (1, 2);
my @names = ("Bob", "Kim");
my @ages = (35, 27);
my @notes = ("I like dogs", "I like birds");

my $sth = $con->prepare("INSERT INTO lcs_people(id, name, age, notes) VALUES (?, ?, ?, ?)");
my $tuples = $sth->execute_array(
 { ArrayTupleStatus => \my @tuple_status }, \@ids, \@names, \@ages, \@notes,);
if ($tuples) {
 print "Successfully inserted $tuples records\n";
} else {
 print "Insert failed\n";
}

# Insert default rows
my @ids = (1, 2);
my @names = ("Duke", "Pepe");
my @owners = (1, 2);
my @types = ("dog", "bird");

my $sth = $con->prepare("INSERT INTO lcs_pets(id, name, owner, type) VALUES (?, ?, ?, ?)");
my $tuples = $sth->execute_array(
 { ArrayTupleStatus => \my @tuple_status }, \@ids, \@names, \@owners, \@types,);
if ($tuples) {
 print "Successfully inserted $tuples records\n";
} else {
 print "Insert failed\n";
}

$con->disconnect;
Boilerplate template

The template we will be using is:

use strict;
use DBI;
my $connectString=$ENV{'db_connect'};

sub get_all_rows {
 my $label = $_[0];
 # Query all rows
 my $con = DBI->connect( 'dbi:Oracle:', $connectString, '') ||
 die "Database connection not made: $DBI::errstr";
 $con->{RaiseError} = 1; # set the connection to raise errors
 my $sth = $con->prepare("select id, name, age, notes from lcs_people order by id");
 $sth->execute;

 print "\n $label: \n";
 while (my @row = $sth->fetchrow_array){
   print " @row\n";
 }
 print "\n";

 $con->disconnect;
}

my $con = DBI->connect( 'dbi:Oracle:', $connectString, '') || die "Database connection not made: $DBI::errstr";
$con->{RaiseError} = 1; # set the connection to raise errors

get_all_rows('Original Data');

# Your code here

get_all_rows('New Data');

For each exercise, replace the “# Your code here” line with your code.

Simple insert

We will perform a simple insert that adds a single record into the lcs_people table.  These are the steps performed in the code snippet below.

  • Prepare a SQL INSERT statement, specifying the table and columns to insert the data.
  • Bind the three parameters to their values.  (See the R part of this series for an explanation of bind variables)
  • Execute the statement.
my $sth = $con->prepare("insert into lcs_people(name, age, notes) values (:name, :age, :notes)");
$sth->bind_param( ":name","Sandy");
$sth->bind_param( ":age",31);
$sth->bind_param( ":notes","I like horses");
$sth->execute;

When I run this code in my Perl session, I see:

 Original Data: 
 1 Bob 35 I like dogs
 2 Kim 27 I like birds

 New Data: 
 1 Bob 35 I like dogs
 2 Kim 27 I like birds
 3 Sandy 31 I like horses

You’ll notice in the bullet points above, I did not commit.  The DBD::Oracle driver is set to auto commit by default.  If you plan to process multiple dependent transactions you may want to disable AutoCommit.

What is a transaction?

When you execute Data Manipulation Language or DML statements, such as the insert I use in this post, those changes are only visible to your current connection or session.

Those changes will not be visible to other sessions (even another session connected to the same schema in which the changes were made) until you commit your changes. That step makes it “permanent” in the database, and available for everyone else to see (and possibly change in a future transaction).  This also allows you to roll back a series of uncommitted transactions if one of the later transactions fails and it would cause data problems for the previous transactions.

Extra Fun 1 & 2

1.  Insert more than 1 row .

Using data for ‘Rob’, 37, ‘I like snakes’ and ‘Cheryl’, 41, ‘I like monkeys’ Your results should be:

 Original Data: 
 1 Bob 35 I like dogs
 2 Kim 27 I like birds
 3 Sandy 31 I like horses

 New Data: 
 1 Bob 35 I like dogs
 2 Kim 27 I like birds
 3 Sandy 31 I like horses
 4 Rob 37 I like snakes
 5 Cheryl 41 I like monkeys
Answer

2.  Verify that a second connection cannot see your changes till after the commit.

Using data for ‘Suzy’, 31, ‘I like rabbits’ and assuming that you did the previous exercise your results should be:

 Original Data: 
 1 Bob 35 I like dogs
 2 Kim 27 I like birds
 3 Sandy 31 I like horses
 4 Rob 37 I like snakes
 5 Cheryl 41 I like monkeys

 New connection after insert: 
 1 Bob 35 I like dogs
 2 Kim 27 I like birds
 3 Sandy 31 I like horses
 4 Rob 37 I like snakes
 5 Cheryl 41 I like monkeys

 Same connection: 
 1 Bob 35 I like dogs
 2 Kim 27 I like birds
 3 Sandy 31 I like horses
 4 Rob 37 I like snakes
 5 Cheryl 41 I like monkeys
 6 Suzy 31 I like rabbits

 New connection after commit: 
 1 Bob 35 I like dogs
 2 Kim 27 I like birds
 3 Sandy 31 I like horses
 4 Rob 37 I like snakes
 5 Cheryl 41 I like monkeys
 6 Suzy 31 I like rabbits

 New Data: 
 1 Bob 35 I like dogs
 2 Kim 27 I like birds
 3 Sandy 31 I like horses
 4 Rob 37 I like snakes
 5 Cheryl 41 I like monkeys
 6 Suzy 31 I like rabbits

Notice that after the insert, the connection that made the insert can see Suzy but the second connection can’t.

After the commit, both connections see Suzy.

Answer
Reset the data

Now is a good time to run reset_data.perl.

Using Identity Columns

You may have noticed that the id column is not passed in, but is automatically set sequentially.  Prior to Oracle Database 12c, this was accomplished using a sequence and a trigger.

In 12c, this can be accomplished by using an Identity Column.

 CREATE TABLE lcs_people (
 id NUMBER GENERATED BY DEFAULT AS identity,
 ....
 You can find more information on identity columns here(pdf).
Returning data after an insert
 Sometimes we need to perform additional operations after an insert using data generated by the database, such as the identity column above.  For example, let’s add a person and a pet for them.

We could run an insert then select the value back using the name.  But if the name is not unique we’ll have a problem.  This is where the RETURNING clause is helpful.

We will perform an insert that adds a single record into the lcs_people table. Then using the returned id we will add a pet.  These are the steps performed in the code snippet below.

  • Prepare a SQL INSERT statement, specifying the table and columns to insert the people data.
  • Bind the three “values” parameters to their values.
  • Bind the id parameters to a new variable $new_id using bind_param_inout .
  • Execute the statement returning the id into new_id.
  • Prepare a SQL INSERT statement, specifying the table and columns to insert the pet data.
  • Bind the id parameter to the $new_id value.
  • Execute the statement.
  • Print the new_id value.
  • Prepare a SQL statement.
  • Bind the owner parameter to the $new_id value.
  • Execute the statement.
  • Print the results with a little decoration text.
my $sth = $con->prepare("insert into lcs_people(name, age, notes) values (:name, :age, :notes) returning id into :id");
$sth->bind_param( ":name","Sandy");
$sth->bind_param( ":age",31);
$sth->bind_param( ":notes","I like horses");
$sth->bind_param_inout(":id", \my $new_id, 99);
$sth->execute;

my $sth = $con->prepare("insert into lcs_pets (name, owner, type) values (:name, :owner, :type)");
$sth->bind_param( ":name","Big Red");
$sth->bind_param( ":owner", $new_id);
$sth->bind_param( ":type","horse");
$sth->execute;

print " Our new value is: $new_id\n";

$sth = $con->prepare("select name, owner, type from lcs_pets where owner = :owner");
$sth->bind_param(":owner", $new_id);
$sth->execute;

print "\n Sandy\'s pets:\n";
while (my @row = $sth->fetchrow_array){
 print " @row\n";
}
print "\n";

When I run this code in my Perl session, I see:

 Original Data: 
 1 Bob 35 I like dogs
 2 Kim 27 I like birds

 Our new value is: 3

 Sandy's pets:
 Big Red 3 horse

 New Data: 
 1 Bob 35 I like dogs
 2 Kim 27 I like birds
 3 Sandy 31 I like horses

Notice the new value, the owner in Sandy’s pets and Sandy’s id in the New Data are all 3 .

Extra Fun 3

3.  Insert Sandy again but return her id and name.

Your results should be:

 Original Data: 
 1 Bob 35 I like dogs
 2 Kim 27 I like birds
 3 Sandy 31 I like horses

 Our new id is: 23 name: Sandy

 New Data: 
 1 Bob 35 I like dogs
 2 Kim 27 I like birds
 3 Sandy 31 I like horses
 4 Sandy 31 I like horses

Notice that (3, ‘Sandy’..) is still there along with our new (4, ‘Sandy’..) but the returned id is 4.  It should return the new id each time you run it.

Answer
 Reset the data

Now is a good time to run reset_data.perl.

Insert more than 1 row

As mentioned above, when you want to insert multiple rows, running multiple insert statements is inefficient and makes multiple trips to the database so instead, we will use execute_array.  In some databases, execute_array is simply a shortcut that will call execute for each record.  However, if your database is capable of bulk processing like Oracle is, the driver will create a much more efficient bulk transaction.

We will perform an insert that adds two records into the lcs_people table.  These are the steps performed in the code snippet below.

  • Create an array for the each column populated with the data for that column.  The longest array will be used to determine the number of transactions if there are any shorter arrays they will be padded with NULL.
  • Prepare a SQL INSERT statement, specifying the table and columns to insert the people data.  Notice we’re using positional bind variables this time.
  • Use execute_array to execute the  statement.  We aren’t accessing any of the execute_array attributes “{}.” Bind the three arrays in order of use.
  • Print the number of records inserted using $tuples, if $tuples is unknown the transaction failed.
my @names = ("Sandy", "Suzy");
my @ages = (31, 29);
my @notes = ("I like horses", "I like rabbits");

my $sth = $con->prepare("INSERT INTO lcs_people(name, age, notes) VALUES (?, ?, ?)");
my $tuples = $sth->execute_array({}, \@names, \@ages, \@notes,);
if ($tuples) {
 print " Successfully inserted $tuples records\n";
} else {
 print " Insert failed\n";
}

When I run this code in my Perl session, I see:

 Original Data: 
 1 Bob 35 I like dogs
 2 Kim 27 I like birds

 Successfully inserted 2 records

 New Data: 
 1 Bob 35 I like dogs
 2 Kim 27 I like birds
 3 Sandy 31 I like horses
 4 Suzy 29 I like rabbits
Some things you could try
  • Loop through an array of people and insert each one returning its id.  Using that id add multiple pets with execute_array.
  • Create a large array of people.  Time the difference between looping through single inserts and using execute_array.

Series sections

Initial Setup
Create records
Retrieve records
Update records
Delete records

Select (cRud) using Ruby-OCI8

In this post, we’re going to take a look at the R in CRUD: Retrieve.

We will be using the ruby-oci8 driver to retrieve some data from the database tables, using the connection object created in the Initial Setup section of the first post in this series.

Simple query

We will perform a simple query that pulls all of the records in no particular order.  Here are the steps we’ll follow in the code snippet below.

  1. Create the connection object.  We will use this object to perform our database operations.
  2. Define the SQL SELECT statement, specifying the columns desired from the table.
  3. Create a cursor by parsing the statement.
  4. Execute the cursor.
  5. Fetch and loop through the rows.
  6. Print each row.
# Query all rows
con = OCI8.new(connectString)
statement = 'select id, name, age, notes from lcs_people'
cursor = con.parse(statement)
cursor.exec
cursor.fetch() {|row|
 print row
}

When I run this code in my Ruby session, I see:

[#<BigDecimal:15bcb00,'0.1E1',9(18)>, "Bob", #<BigDecimal:15bc790,'0.35E2',9(18)>, "I like dogs"][#<BigDecimal:15bd1b8,'0.2E1',9(18)>, "Kim", #<BigDecimal:193bf60,'0.27E2',9(18)>, "I like birds"]

This is not real pretty, so from here on we’ll use printf.

printf "Id: %d, Name: %s, Age: %d, Notes: %s\n", row[0], row[1], row[2], row[3]

Much better:

select1pretty

Id: 1, Name: Bob, Age: 35, Notes: I like dogs
Id: 2, Name: Kim, Age: 27, Notes: I like birds

Extra Fun 1

Modify the statement to order by age.  When you’re done the results should be:

Id: 2, Name: Kim, Age: 27, Notes: I like birds
Id: 1, Name: Bob, Age: 35, Notes: I like dogs
Answer
Select specific rows

Now suppose I only want to see the data for Kim. I want, therefore, to restrict the rows returned by the SELECT. This is done with a WHERE clause. There are several ways to do this.

We could just put the where clause in the statement and it would work.

statement = "select id, name, age, notes from lcs_people where name = 'Kim'"

However, we want to choose the name at run time and store it in a variable called person_name.  You could accept the value in as an argument passed into a function, but we’ll just set a variable to keep it simple.

person_name = 'Kim'

It is possible to simply concatenate the value into the statement.

statement = "select id, name, age, notes from lcs_people where name = '#{person_name}'"

This is very dangerous and opens our code to a SQL Injection attack.  You can follow that link for more information, but we won’t be going into detail in this series.  Just know that you should, generally, never allow end user input to be fed directly into a dynamic SQL statement.

A much safer way to pass external values into the SQL statement is by using bind variables with prepared statements.

You have a couple different options:

Positional:
statement = "select id, name, age, notes from lcs_people where name = :1 and age = :2"
cursor = con.parse(statement)
cursor.bind_param(1, 'Bob')
cursor.bind_param(2, 35)

statement = "select id, name, age, notes from lcs_people where name = :2 and age = :1"
cursor = con.parse(statement)
cursor.bind_param(1, 'Bob')
cursor.bind_param(2, 35)

Notice the :1 and :2 are switched in the two examples. With a positional statement, the labels do not matter, it could just as well have been :1 and :something. What matters is the first :variable in the statement will be assigned the value of the bind_param with the index of 1, the second the value of index 2 and so on.

Positional bind parameters will us an integer as the key in bind_param().

Named:
statement = "select id, name, age, notes from lcs_people where name = :name and age = :age"
cursor = con.parse(statement)
cursor.bind_param('name', 'Bob')
cursor.bind_param('age', 35)

statement = "select id, name, age, notes from lcs_people where name = :age and age = :name"
cursor = con.parse(statement)
cursor.bind_param('age', 'Bob')
cursor.bind_param('name', 35)

With this method, the :name variable will be assigned the value of ‘name’ in the provided key value set.

In the second example, I switched the labels in the SQL, and I also had to switch the keys in the bind_parameter calls so the correct value is still used.

Notice, in both examples, that we do not wrap the bind variable for the name with quotes.  This is handled automatically when the statement is prepared for execution.

Example:
  1. Create the connection object.
  2. Create the person_name variable and assign it a value of ‘Kim’.
  3. Define the SQL SELECT statement, specifying the columns desired from the table.
  4. Create a cursor by parsing the statement.
  5. Bind the value of person_name to :name.
  6. Execute the cursor.
  7. Fetch and loop through the rows.
  8. Print each row.
# Query for Kim
con = OCI8.new(connectString)

person_name = 'Kim'
statement = "select id, name, age, notes from lcs_people where name=:name"
cursor = con.parse(statement)
cursor.bind_param('name', person_name)
cursor.exec
cursor.fetch() {|row|
 printf "Id: %d, Name: %s, Age: %d, Notes: %s\n", row[0], row[1], row[2], row[3]
}

This will return only the data for Kim:

Id: 2, Name: Kim, Age: 27, Notes: I like birds
Extra Fun 2

Modify the statement and variable to get the people older than 30.  When you’re done the results should be:

Id: 1, Name: Bob, Age: 35, Notes: I like dogs
Answer

In this section, we took a look at some basic query functionality.  When you experiment with more complex queries, if you run into problems leave a comment here or on twitter and we’ll find an answer together.

Some things you could try
  • Join the lcs_people and lcs_pets table to get the people and their pets
  • Only retrieve the person’s name and age
  • Change the order to display in descending order.

Hint – If you have trouble getting a query to run in your code, try running it in SQL Plus or another database console tool.  This will help determine if the problem is with the query or the code.

Series sections

Initial Setup
Create records
Retrieve records
Update records
Delete records

Select (cRud) using Perl and DBD::ORACLE

In this post, we’re going to take a look at the R in CRUD: Retrieve.

We will be using the DBD::Oracle driver to retrieve some data from the database tables, using the connection object created in the Initial Setup section of the first post in this series.

Simple query

We will perform a simple query that pulls all of the records in no particular order.  Here are the steps we’ll follow in the code snippet below.

  1. Create the connection object and set it to raise errors.  We will use this object to perform our database operations.
  2. Prepare the SQL SELECT statement, specifying the columns desired from the table.
  3. Execute the statement.
  4. Fetch the results and dump them to $fh.
  5. Disconnect.
# Query all rows
my $con = DBI->connect( 'dbi:Oracle:', $connectString, '');
$con->{RaiseError} = 1; # set the connection to raise errors

my $sth = $con->prepare("select id, name, age, notes from lcs_people");
$sth->execute;
DBI::dump_results($sth);

$con->disconnect;

When I run this code in my Perl session, I see:

'1', 'Bob', '35', 'I like dogs'
'2', 'Kim', '27', 'I like birds'
2 rows
Extra Fun 1

Modify the statement to order by age.  When you’re done the results should be:

'2', 'Kim', '27', 'I like birds'
'1', 'Bob', '35', 'I like dogs'
2 rows
Answer
Select specific rows

Now suppose I only want to see the data for Kim. I want, therefore, to restrict the rows returned by the SELECT. This is done with a WHERE clause. There are several ways to do this.

We could just put the where clause in the statement and it would work.

my $sth = $con->prepare("select id, name, age, notes from lcs_people where name = 'Kim'");

However, we want to choose the name at run time and store it in a variable called person_name.  You could accept the value in as an argument passed into a function, but we’ll just set a variable to keep it simple.

my $person_name = 'Kim';

It is possible to simply concatenate the value into the statement.

my $sth = $con->prepare("select id, name, age, notes from lcs_people where name= '${person_name}'");

This is very dangerous and opens our code to a SQL Injection attack.  You can follow that link for more information, but we won’t be going into detail in this series.  Just know that you should, generally, never allow end user input to be fed directly into a dynamic SQL statement.

A much safer way to pass external values into the SQL statement is by using bind variables with prepared statements.

You have a couple different options:

Placeholders:
my $sth = $con->prepare("select id, name, age, notes from lcs_people where name = ? and age = ?");
$sth->bind_param(1,'Bob');
$sth->bind_param(2, 35);

my $sth = $con->prepare("select id, name, age, notes from lcs_people where name = ? and age = ?");
$sth->bind_param(2, 35);
$sth->bind_param(1,'Bob');

Notice the bind_param(1,  and bind_param(2, are switched in the two examples.  With a placeholders statement, you use a ? to indicate where the bind variable value goes, then when you assign the bind_param you indicate which placeholder to assign the value to.

Named:
my $sth = $con->prepare("select id, name, age, notes from lcs_people where name = :name and age = :age");
$sth->bind_param( ":name",'Bob');
$sth->bind_param( ":age", 35);

my $sth = $con->prepare("select id, name, age, notes from lcs_people where name = :name and age = :age");
$sth->bind_param( ":age", 35);
$sth->bind_param( ":name",'Bob');

With this method, the :name variable will be assigned the value of ‘name’ in the provided key value set.

Notice, in both examples, that we do not wrap the bind variable for the name with quotes.  This is handled automatically when the statement is prepared for execution.

Example:
  1. Create the connection object and set it to raise errors.
  2. Assign ‘Kim’ to person_name.
  3. Prepare the SQL statement using a bind variable.
  4. Bind the value of $person_name to :name.
  5. Execute the statement.
  6. Fetch the results and dump them to $fh.
  7. Disconnect.
# Query for Kim
my $con = DBI->connect( 'dbi:Oracle:', $connectString, '');
$con->{RaiseError} = 1; # set the connection to raise errors

my $person_name = 'Kim';
my $sth = $con->prepare("select id, name, age, notes from lcs_people where name=:name ");
$sth->bind_param( ":name",$person_name);

$sth->execute;
DBI::dump_results($sth);

This will return only the data for Kim:

'2', 'Kim', '27', 'I like birds'
1 rows
Extra Fun 2

Modify the statement and variable to get the people older than 30.  When you’re done the results should be:

'1', 'Bob', '35', 'I like dogs'
1 rows
Answer

In this section, we took a look at some basic query functionality.  When you experiment with more complex queries, if you run into problems leave a comment here or on twitter and we’ll find an answer together.

Some things you could try
  • Join the lcs_people and lcs_pets table to get the people and their pets
  • Only retrieve the person’s name and age
  • Change the order to display in descending order.

Hint – If you have trouble getting a query to run in your code, try running it in SQL Plus or another database console tool.  This will help determine if the problem is with the query or the code.

Series sections

Initial Setup
Create records
Retrieve records
Update records
Delete records

Basic CRUD operations using Perl and DBD::Oracle

In this series, we’re going to take a look at performing CRUD (Create Retrieve Update Delete) operations using the DBD::Oracle driver.

A good ORM will handle most of your needs.

An ORM tool can handle many of the repetitive processes when interfacing with a database.  Your project might call for an ORM tool such as DBIx::Class.  No doubt about it,  a good ORM can come in very handy.  An ORM application will typically have a function for passing in raw SQL if needed, so you may not need to go straight to the driver.

Why learn to use the driver directly?

An ORM brings its own, different complexity to a project.  It may be overkill for some projects.  There are also times when a specific task is just different enough that an ORM may not be able to help, or its application to your requirements become so complex that your code becomes difficult to maintain.

And if you’re like me, it’s hard to be satisfied with a black box approach.  You want to know more about how your tools work and you want to have options, just in case.

Martin Fowler said “Mapping to a relational database involves lots of repetitive, boiler-plate code.  A framework that allows me to avoid 80% of that is worthwhile even if it is only 80%.”

When you have enough knowledge to implement direct CRUD operations, you are in a better position to choose the right tool for the right job.

Common Setup

All examples in this series will use the same database objects and connection information.

Creating the Database Objects

The following can be used to setup the initial tables we’ll use.  Please make sure you’re connected to a schema in which you can safely execute commands like these.

CREATE TABLE LCS_PEOPLE (
 id NUMBER GENERATED BY DEFAULT AS identity,
 name VARCHAR2(20),
 age NUMBER,
 notes VARCHAR2(100)
)
/

ALTER TABLE LCS_PEOPLE
ADD CONSTRAINT PK_LCS_PEOPLE PRIMARY KEY ("ID")
/

CREATE TABLE LCS_PETS (
 id NUMBER GENERATED BY DEFAULT AS IDENTITY,
 name VARCHAR2(20),
 owner NUMBER,
 type VARCHAR2(100)
)
/

ALTER TABLE LCS_PETS ADD CONSTRAINT PK_LCS_PETS PRIMARY KEY ("ID")
/

ALTER TABLE LCS_PETS ADD CONSTRAINT FK_LCS_PETS_OWNER FOREIGN KEY ("OWNER") REFERENCES "LCS_PEOPLE" ("ID")
/

INSERT INTO LCS_PEOPLE (name, age, notes)
 VALUES ('Bob', 35, 'I like dogs')
/

INSERT INTO LCS_PEOPLE (name, age, notes)
 VALUES ('Kim', 27, 'I like birds')
/

INSERT INTO LCS_PETS (name, owner, type)
 VALUES ('Duke', 1, 'dog')
/

INSERT INTO LCS_PETS (name, owner, type)
 VALUES ('Pepe', 2, 'bird')
/

COMMIT
/
 Making the Connection
  1. use strict
  2. use the DBD::Oracle driver.
  3. Get the connection string from the environment variable.
  4. Create the connection object.
  5. Set the connection to raise errors.
use strict;
use DBI;
my $connectString=$ENV{'db_connect'};
my $con = DBI->connect( 'dbi:Oracle:', $connectString, '') || die "Database connection not made: $DBI::errstr";
$con->{RaiseError} = 1; # set the connection to raise errors

We will include this code section with all examples and use the connection object “con” throughout the series.

Cleanup

To  clean up the database when you are finished with the series, you just need to drop the two tables.  Please make sure you’re connected to the correct schema where you created the tables.

drop table LCS_PETS
/

drop table LCS_PEOPLE
/
Guide to Perl DBD::Oracle CRUD Series

Initial Setup
Create records
Retrieve records
Update records
Delete records

Basic CRUD operations using Ruby-OCI8

In this series, we’re going to take a look at performing CRUD (Create Retrieve Update Delete) operations using the ruby-oci8 driver.

A good ORM will handle most of your needs.

An ORM tool can handle many of the repetitive processes when interfacing with a database.  Your project might call for an ORM tool such as ActiveRecord.  No doubt about it,  a good ORM can come in very handy.  An ORM application will typically have a function for passing in raw SQL if needed, so you may not need to go straight to the driver.

Why learn to use the driver directly?

An ORM brings its own, different complexity to a project.  It may be overkill for some projects.  There are also times when a specific task is just different enough that an ORM may not be able to help, or its application to your requirements become so complex that your code becomes difficult to maintain.

And if you’re like me, it’s hard to be satisfied with a black box approach.  You want to know more about how your tools work and you want to have options, just in case.

Martin Fowler said “Mapping to a relational database involves lots of repetitive, boiler-plate code.  A framework that allows me to avoid 80% of that is worthwhile even if it is only 80%.”

When you have enough knowledge to implement direct CRUD operations, you are in a better position to choose the right tool for the right job.

Common Setup

All examples in this series will use the same database objects and connection information.

Creating the Database Objects

The following can be used to setup the initial tables we’ll use.  Please make sure you’re connected to a schema in which you can safely execute commands like these.

CREATE TABLE LCS_PEOPLE (
 id NUMBER GENERATED BY DEFAULT AS identity,
 name VARCHAR2(20),
 age NUMBER,
 notes VARCHAR2(100)
)
/

ALTER TABLE LCS_PEOPLE
ADD CONSTRAINT PK_LCS_PEOPLE PRIMARY KEY ("ID")
/

CREATE TABLE LCS_PETS (
 id NUMBER GENERATED BY DEFAULT AS IDENTITY,
 name VARCHAR2(20),
 owner NUMBER,
 type VARCHAR2(100)
)
/

ALTER TABLE LCS_PETS ADD CONSTRAINT PK_LCS_PETS PRIMARY KEY ("ID")
/

ALTER TABLE LCS_PETS ADD CONSTRAINT FK_LCS_PETS_OWNER FOREIGN KEY ("OWNER") REFERENCES "LCS_PEOPLE" ("ID")
/

INSERT INTO LCS_PEOPLE (name, age, notes)
 VALUES ('Bob', 35, 'I like dogs')
/

INSERT INTO LCS_PEOPLE (name, age, notes)
 VALUES ('Kim', 27, 'I like birds')
/

INSERT INTO LCS_PETS (name, owner, type)
 VALUES ('Duke', 1, 'dog')
/

INSERT INTO LCS_PETS (name, owner, type)
 VALUES ('Pepe', 2, 'bird')
/

COMMIT
/
 Making the Connection
  1. require the ruby-oci8 driver.
  2. Get the connection string from the environment variable.
  3. Create the connection object.
require 'oci8'
connectString = ENV['db_connect'] 
con = OCI8.new(connectString)

We will include this code section with all examples and use the “con” connection object “con” throughout the series.

Cleanup

To  clean up the database when you are finished with the series, you just need to drop the two tables.  Please make sure you’re connected to the correct schema where you created the tables.

drop table LCS_PETS
/

drop table LCS_PEOPLE
/
Guide to Ruby-OCI8 CRUD Series

Initial Setup
Create records
Retrieve records
Update records
Delete records