MySQL - auto decrementing value

Question

Let\'s say that I\'ve got a table, like that (id is auto-increment):

id | col1 | col2
1  | \'msg\'| \'msg\'
2  | \'lol\'| \'lol2\'
3  | \'xxx\'| \'x\'
         


        

Answer 1

It is not good practice to change the value of an auto_increment column. However, if you are sure you want to, the following should help.

If you are only deleting a single record at a time, you could use a transaction:

START TRANSACTION;
DELETE FROM table1 WHERE id = 2;
UPDATE table1 SET id = id - 1 WHERE id > 2;
COMMIT;

However if you delete multiple records, you will have to drop the column and re-add it. It is probably not guaranteed to put the rows in the same order as previously.

ALTER TABLE table1 DROP id;
ALTER TABLE table1 ADD id INTEGER NOT NULL AUTO_INCREMENT;

Also, if you have data that relies on these IDs, you will need to make sure it is updated.