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How to use a Temporary Table and ALTER TABLE to Add Identity In SQL

2. Create a Temporary Table with Identity Column and Copy Data

Conclusion

In this approach, we’ll create a temporary table, copy data from the original table, add an identity column using ALTER TABLE, and then copy the data back.

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;

UPDATE temp_table_name
SET column_name = (SELECT COUNT(*) FROM original_table WHERE original_table.primary_key <= temp_table_name.primary_key);

ALTER TABLE temp_table_name
ADD PRIMARY KEY (column_name);

INSERT INTO temp_table_name (column1, column2, ..., column_name)
SELECT column1, column2, ..., column_name 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 and Row Counting in SQLite

CREATE TEMPORARY TABLE  temp_products  AS
SELECT id, name, price, NULL AS row_id FROM products ;

ALTER TABLE  temp_products 
ADD COLUMN row_id INTEGER;

UPDATE  temp_products 
SET row_id = (SELECT COUNT(*) FROM products WHERE products.id <=temp_products.id);

ALTER TABLE  temp_products 
ADD PRIMARY KEY (row_id);

INSERT INTO  temp_products  (id, name, price ,row_id)
SELECT id, name, price, row_id FROM products ;

DROP TABLE products;

ALTER TABLE temp_products  RENAME TO products;

Output:

Using a Temporary Table and ALTER TABLE to Add Identity(Output)

Explanation:

  • A temporary table temp_products is created with the same schema as the original products table, including a nullable identity column named row_id.
  • The identity values are updated based on the row position in the original products table.
  • The temporary table is altered to set the identity column as the primary key.
  • Data from the temporary table is copied into the original products 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

Similar Reads

Understanding Identity Columns

Identity columns in SQLite automatically assign unique, auto-incrementing values to each row in a table, often serving as primary keys. Unlike SQL Server, SQLite doesn’t offer native identity column support. Developers typically implement this functionality using techniques like AUTOINCREMENT or row counting to ensure data integrity and efficient data management....

How to Add an Identity to An Existing Column in SQLite

To add an identity to an existing column in SQLite, developers can use ALTER TABLE with AUTOINCREMENT, create a temporary table, copy data, add an identity column, or update identity values based on row positions. We will explore the three approaches:...

Setting up an Environment

Different approaches to add identity to an existing column are:...

1. Using ALTER TABLE with AUTOINCREMENT

In this approach, we’ll utilize the ALTER TABLE statement along with the AUTOINCREMENT keyword to add an identity column to an existing table....

2. 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....

3. Using a Temporary Table and ALTER TABLE to Add Identity

In this approach, we’ll create a temporary table, copy data from the original table, add an identity column using ALTER TABLE, and then copy the data back....

Conclusion

While adding an identity column to an existing table in SQLite is easy and takes just a few simple steps, it is imperative to pay close attention to data integrity. The procedure detailed in this article along with some care will help you to add an identity column to your SQLite database and improve the structure of your tables. Keep in mind to always take a backup of your database before making any structural changes and test your changes thoroughly to make sure they are in compliance with your requirements. Through a proper knowledge of SQLite functionalities and the appropriate SQL commands, you can skillfully maintain and optimize your database schema and data management workflows....

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#SQLite Query #Databases #SQLite

2. Create a Temporary Table with Identity Column and Copy Data

Conclusion