I don't understand what you mean by saying each join creates a cartesian product. Join criteria avoid this. If I left outer join 7 rows on table A and 5 on table B and join on a unique key then I still only get 7 rows, not the cartesian product of 7x5 rows. I query across a dozen or more tables on a regular basis with aggregates, window functions, with statements, having clauses and so on. Performance is rarely a problem.