Question

Using PHP and MySQL, I have a query that will look something like this:

UPDATE mytable 
   SET status='$newstatus' 
 WHERE (col1='$col1[0]'AND col2='$col2[0]') 
   OR (col1='$col1[1]'AND col2='$col2[1]') 
   OR (...);

I actually need to record the current ‘status’ of each of these rows before the update. Do I need to do a separate SELECT before this, or can (should / how would) I combine the two queries?

Answer 1

You cannot get that from this query (you could only get number of affected rows, but that’s it). If you need that, you shall first do SELECT on your conditions like:

SELECT `id` FROM `mytable`
WHERE (`col1`='$col1[0]' AND `col2`='$col2[0]')
   OR (`col1`='$col1[1]' AND `col2`='$col2[1]')
   OR (...)

and then do UPDATE with WHERE using fetched ids. I do not recommend doing UPDATE with your current WHERE clause as in meantime (between your SELECT and UPDATE) db content could change, so you could be UPDATING different rows that you had SELECTed. Or use table locking (but I do not think it makes sense here).