Updating one php table w/multiple tables

[webstu]

How do I update one table (namely one record in that table) using info from multipe tables. I tried using a join clause but it didn't seem to work. Heres my basic code.

$query = "update rooms,room_def set rooms.vacancy=room_def.capacity where rooms.bldg_code=room_def.bldg_code and rooms.room_number=room_def.room_number";

that's the query...is it correct?

Thanks

WebStu

[Anon]

you need to first select information out of one table, and then use that to do your update. make two queries because mysql won't let you do one on an update.