How to Remove Primary Keys from Columns in MySQL While Keeping Auto-Increment?

Removing Primary Keys in MySQL

Question:

How can you drop primary keys from specific columns in a MySQL table while maintaining an auto-incrementing id as the primary key?

Response:

Background:

In MySQL, an auto-incrementing column must be defined as part of an index, making it difficult to remove primary keys from other columns without errors.

Solution:

To remove primary keys from specific columns, follow these steps:

1. Disable Auto-Increment: Use the ALTER TABLE statement to modify the id column's data type to INT and remove the NOT NULL constraint.

ALTER TABLE user_customer_permission MODIFY id INT;

2. Drop Primary Key: Once the auto-increment property is removed, use the ALTER TABLE statement to drop the primary key constraint from the user_customer_id and permission_id columns.

ALTER TABLE user_customer_permission DROP PRIMARY KEY;

Additional Considerations:

• The original composite primary key spanned all three columns, so the id column may not be unique.
• If id is unique, you can re-enable the primary key and auto-increment properties on the id column.

ALTER TABLE user_customer_permission MODIFY id INT NOT NULL PRIMARY KEY AUTO_INCREMENT;

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