I am trying to insert a new row and set the customer_id with max()+1. The reason for this is the table already has a auto_increatment on another column named id and the tabl
You can't do it in a single query, but you could do it within a transaction. Do the initial MAX() select and lock the table, then do the insert. The transaction ensures that nothing will interrupt the two queries, and the lock ensures that nothing else can try doing the same thing elsewhere at the same time.