Remove Primary Key in MySQL

Without an index, maintaining an autoincrement column becomes too expensive, that’s why MySQL requires an autoincrement column to be a leftmost part of an index.

You should remove the autoincrement property before dropping the key:

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

Note that you have a composite PRIMARY KEY which covers all three columns and id is not guaranteed to be unique.

If it happens to be unique, you can make it to be a PRIMARY KEY and AUTO_INCREMENT again:

ALTER TABLE user_customer_permission MODIFY id INT NOT NULL PRIMARY