Mysql Innodb: Autoincrement non-Primary Key

Question

Is it possible to auto-increment a non-Primary Key?

Table \"book_comments\"

book_id     medium_int
timestamp   medium_int
user_id     medium_int
vote         


        

Answer 1

You've existing table. If you already gave a primary key to comment_id and the only purpose is to set auto_increment. You can drop the primary key to that column. MySQL allows a column with any key property can access auto_increment. So better try an index or unique key to comment_id like below.

1.Remove Primary Key

ALTER TABLE `book_comments` MODIFY `comment_id` INT(5) NOT NULL;

ALTER TABLE `book_comments` DROP PRIMARY KEY ;

2. Add AUTO_INCREMENT with UNIQUE_KEY property.

ALTER TABLE 'brand_keywords' CHANGE COLUMN 'comment_id' 'comment_id' INT(5) NOT NULL AUTO_INCREMENT UNIQUE;