Finding the next available id in MySQL

Question

I have to find the next available id (if there are 5 data in database, I have to get the next available insert place which is 6) in a MySQL database. How can I do that? I h

Answer 1

If you want to select the first gap, use this:

SELECT  @r
FROM    (
        SELECT  @r := MIN(id) - 1
        FROM    t_source2
        ) vars,
        t_source2
WHERE   (@r := @r + 1) <> id
ORDER BY
        id
LIMIT   1;

There is an ANSI syntax version of the same query:

SELECT  id
FROM    mytable mo
WHERE   (
        SELECT  id + 1
        FROM    mytable mi
        WHERE   mi.id < mo.id
        ORDER BY
                mi.id DESC
        LIMIT 1
        ) <> id
ORDER BY
        id,
LIMIT   1

however, it will be slow, due to optimizer bug in MySQL.