What you’re trying to do sounds dangerous, as that’s not the intended use of AUTO_INCREMENT
.
If you really want to find the lowest unused key value, don’t use AUTO_INCREMENT
at all, and manage your keys manually. However, this is NOT a recommended practice.
Take a step back and ask “why you need to recycle key values?” Do unsigned INT
(or BIGINT
) not provide a large enough key space?
Are you really going to have more than 18,446,744,073,709,551,615
unique records over the course of your application’s lifetime?