How to fill in the “holes” in auto-increment fields?

Question

I\'ve read some posts about this but none cover this issue.

I guess its not possible, but I\'ll ask anyway.

I have a table with more than 50.000 registers. I

Answer 1

You generally don't need to care about gaps. If you're getting to the end of the datatype for the ID it should be relatively easy to ALTER the table to upgrade to the next biggest int type.

If you absolutely must start filling gaps, here's a query to return the lowest available ID (hopefully not too slowly):

SELECT MIN(table0.id)+1 AS newid
FROM table AS table0
LEFT JOIN table AS table1 ON table1.id=table0.id+1
WHERE table1.id IS NULL

(remember to use a transaction and/or catch duplicate key inserts if you need concurrent inserts to work.)