On Tue, Sep 1, 2009 at 10:55 AM, tedd<t...@sperling.com> wrote: > > I fully understand WHERE, it's understanding how JOIN's simplify things.
1. Joins make your sql more readable (and are a substatement to the FROM clause, and should be indented) 2. When you use the WHERE clause, it is easy to accidentally do a cartesian join, and select bazillions of rows during development. 3. You can change to a LEFT join as needed. Since you can't do a left join in the where clause, you might as well use the JOIN syntax everywhere. Consider SELECT user.name, COUNT(post.post_id) as post_count FROM user LEFT JOIN post USING user_id GROUP BY 1 vs SELECT user.name, COUNT(post.post_id) as post_count FROM user INNER JOIN post USING user_id GROUP BY 1 The second one can be rewritten using a WHERE clause, but the first one can't. People who don't understand the first query, end up writing stuff like: SELECT user.name, (SELECT COUNT(*) from post WHERE post.user_id=user.user_id) as post_count FROM user -john campbell _______________________________________________ New York PHP User Group Community Talk Mailing List http://lists.nyphp.org/mailman/listinfo/talk http://www.nyphp.org/show_participation.php
