On Tue, Sep 1, 2009 at 8:58 AM, tedd <[email protected]> wrote: > > I need to understand joins much better than I do now because the first query > I fully understand while the second I don't. >
Think of the WHERE clause as the filter. Use it to place restrictions on what information is returned. WHERE price > 50 AND color = 'red' In the previous example you also had things like "vendor.id = product.vendor_id." You aren't using this to filter the data. You are using it to link up two tables. This is where the JOIN clause comes in. For example, if you want a list of products with their associated vendors: FROM products INNER JOIN vendors ON products.vendor_id = vendors.id -- or whatever the fields are called To also link to an optional promotion running for a product: LEFT OUTER JOIN promotions ON products. promotion_id = promotions.id _______________________________________________ New York PHP User Group Community Talk Mailing List http://lists.nyphp.org/mailman/listinfo/talk http://www.nyphp.org/show_participation.php
