Question

I have a table with a primary key, auto_increment ID column. When I delete the row with the highest ID, for instance ID 100, I want to use that ID 100 for a new row only using a mysql trigger. How do I do that?

When I delete, for instance ID 1 AND the highest ID is 100, I don’t want to use ID 1 again.

I do the delete and insert statement with different PHP calls.

Answer 1

Finally I found the right solution for my problem. Thanks to all your suggestions en criticism. Instead of using a trigger, I now use a procedure (thanks for the idea @shubhansh).

This is the create statement for the procedure:

DELIMITER $$

USE `[DATABASE]`$$

DROP PROCEDURE IF EXISTS `[PROCEDURE NAME]`$$

CREATE PROCEDURE `[PROCEDURE NAME]`(deleteID INT(11))
BEGIN
    DECLARE i INTEGER;

    SET @deleteRow = CONCAT('delete from `[TABLE NAME]` WHERE ID = ', deleteID);
    PREPARE a FROM @deleteRow;
    EXECUTE a;

    SET i = (SELECT IFNULL(MAX(ID), 0) FROM `[TABLE NAME]`);
    SET @alterTable = CONCAT('alter table `[TABLE NAME]` auto_increment = ',(i+1));
    PREPARE b FROM @alterTable;
    EXECUTE b;

    END$$

DELIMITER ;

Now I can delete and alter one table in one PHP statement and it is save because the procedure locks the table.