Create a Temporary Table with Identity Column and Copy Data
This approach involves creating a temporary table with an identity column, copying data from the original table, and then renaming the temporary table to replace the original one.
Syntax:
CREATE TEMPORARY TABLE temp_table_name AS
SELECT column1, column2, ..., NULL AS column_name FROM original_table;
ALTER TABLE temp_table_name
ADD COLUMN column_name INTEGER PRIMARY KEY AUTOINCREMENT;
INSERT INTO temp_table_name (column1, column2, ..., column_name)
SELECT column1, column2, ..., NULL FROM original_table;
DROP TABLE original_table;
ALTER TABLE temp_table_name RENAME TO original_table;
Example: Modifying the “Products” Table to Add an Identity Column Using Temporary Tables in SQLite
-- Step1: Create a temprary table with an identity column
CREATE TEMPORARY TABLE temp_products AS
SELECT id, name, price, NULL AS row_id FROM products;
-- Step2: Alter the temporary table to add an identity column named "row_id"
ALTER TABLE temp_products
ADD COLUMN row_id INTEGER PRIMARY KEY AUTOINCREMENT;
-- Step3: Insert data from the original "products" table into the temporary table
INSERT INTO temp_products ( id,name,price,row_id)
SELECT id, name, price, NULL FROM products;
-- Step4: Drop the original "products" table:
DROP TABLE products;
-- Rename the temporary table to replace the original "products" table
ALTER TABLE temp_products RENAME TO products;
Output:
Explanation:
- A temporary table temp_products is created with the same schema as the original products table, including an identity column named row_id.
- Data from the original products table is copied into the temporary table.
- The original products table is dropped, and the temporary table is renamed to replace it.
How to Add an Identity to an Existing Column in SQLite
An identity column as a column added to an existing table in SQLite would probably be a crucial task while database restructuring or when implementing new features. The identity column is provided with a compulsory key with auto-incremented values, which makes the administration of data easier and also enhances database efficiency.
In this article, we will understand the process of configuring the Identity Column to an already existing table in SQLite. We’ll talk about the list of steps, and advantages resulting from identity column utilization, and try to give enough instructions to help developers easily add this feature to their SQLite databases