Question

I have a table indexed on column=ID and it is a 5-digit integer.

It is a very old table and was never auto incremented.

I want to list all unused IDs.

I can do it with a SELECT * ORDER BY statement and then run the result against an incremented for() loop, but I was wondering if anyone knows if a SQL Query Statement to do this within MySQL or if you have a more clever method than the approach I am planning to take.

Thanks

Answer 1

This is the approach I would take.

1. Create a number table going from 1 to n (n being your largest ID). Numbers can be generated using a query such as this.
2. Perform a LEFT JOIN to the number table and fetch only NULL results.

See this demo