Using db_simpleSelect for complex query

Trying to write custom PHP using the db_simpleSelect function, but I want to select from two tables and do a SQL join. When I try it, I get no results. I checked syntax by running the query straight from the DB. Does db_simpleSelect just not like having two tables passed in?

P.S. Here is the syntax:

if($cols=db_simpleSelect(0,$Tt.' t, '.$Tp.' p','t.topic_id, t.topic_title, p.post_text','t.topic_id','=','p.topic_id','t.topic_id DESC',10))

Function name says it all: db_simpleSelect, so it's not a place for executing heavy queries.

Heavy queries are actually not the thing we like in miniBB. They are used only when there is no other way; but in most cases, there is a way to create TWO simple selects instead of ONE, but this will be hundred times FASTER else if you use complex query. It will be definitely executed slowly on large systems and active forums!