Mysql SELECT inside UPDATE

Question

UPDATE forms SET

pos = (SELECT MIN(pos)-1 FROM forms)

WHERE id=$id

This doesn\'t work, error message:

**You can\'t specify target         


        

Answer 1

Your problem is stated plainly in the MySQL manual:

Currently, you cannot update a table and select from the same table in a subquery.

You'll want to use a transaction. Turn AutoCommit off, begin a transaction, then do a SELECT MIN(pos)-1 FROM forms FOR UPDATE, take that result, do the update with it, then commit your transaction.