Automatic temp tables? (3 replies)

This is possibly a very newbie question, but what is the default action for MySQL with regards to storing query data?

I have a situation where a developer created a php application that seems to have a recursion problem. The odd thing is that his search interface will return a result, but at the same time a temporary table is created in the MySQL data directory that begins to fill up with data until the disk is full.

I've observed this happening on a few separate occasions. I've reviewed the code and no where does he specifically create a temporary table.

I need to understand how these temp tables are created and why they do not seem to have a hard size limit or a limit on the query length.