title: How many tables is "too many" in a single SQL SELECT?
body: <p>As a DBA for MS SQL 2000 and 2005, I regularly see giant select queries JOINing 7-10 or even more tables. I find, though, that there is a certain point past which performance tends to suffer, and the query becomes very difficult to debug and/or improve.</p>
  
  <p>So is there a "rule of thumb" for when I should be considering other query methods, like temp tables to hold preliminary results? Or is there a point after which the SQL query optimizer just doesn't do a very good job of figuring out the best plan?</p>