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.
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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.
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# 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:
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# 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.
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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 |
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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:
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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 |
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:
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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.
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.
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CREATE TABLE lcs_people ( id NUMBER GENERATED BY DEFAULT AS identity, .... |
Returning data after an insert
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.
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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" |
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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 |
Extra Fun 3
3. Insert Sandy again but return her id and name.
Your results should be:
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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.
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.
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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 |
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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
thanks for this post, it was really helpful !
Thank you, I’m glad you liked it.