mysql delete pk_id code example
Example 1: mysql change primary key
ALTER TABLE tableName MODIFY COLUMN id INT; /* First you should drop auto increment */
ALTER TABLE tableName DROP PRIMARY KEY; /* Dop primary key */
ALTER TABLE tableName ADD PRIMARY KEY (new_id); /* Set primary key to the new column */
ALTER TABLE tableName MODIFY COLUMN new_id INT AUTO_INCREMENT; /* Set auto increment to the new primary key */
Example 2: mysql drop key
ALTER TABLE tbl_quiz_attempt_master
DROP INDEX `PRIMARY`;