Ever wanted to filter a query_posts call by template? If you're reading this post, you probably have or need to right now. You probably went to the query_posts documentation and scanned for something like "template=foo" and were deeply disappointed. Then maybe, in an act of desperation, you started to trudge around the plugin library. Stop! Stop right there! You don't need a plugin to do this. Everything you need is already in WordPress.
Let's start with a question: how does WordPress associate templates? The answer: as a secret custom field. What's a custom field, you ask? They're those useful little suckers under the content area in the WP editor:
But if the template is a custom field, you ask, then how come I don't see it down there? Well, I just said they're secret. After poking around WP database, I discovered the template for a page is determined by the custom field name
_wp_page_template. My suspicion is that anything with the prefix _wp is hidden from the WP admin area and therefore secret.
Harnessing the awesome power of custom fields
On the bright side, even if you can't see the
_wp_page_template in the custom fields area, I can assure you it's still there. And if it's there, you can use it in any of your nefarious schemes.
Query_posts provides 3 parameters relating to custom fields: meta_key, meta_value, and meta_compare. With those in mind, imagine you have a template called Profile (profile.php), and you want to exclude any page that is a Profile from our query. In order to do that, you'd would make a query_posts call like so:
query_posts(array( 'post_type' => 'page', 'meta_key' => '_wp_page_template', 'meta_value' => 'profile.php', 'meta_compare' => '!=' ));
The main thing to note here is that the template is identified by the name of the PHP file (profile.php) and not by the the name of template (Profile).
Filtering your query_posts query by template is as easy as filtering by any custom field. No plugin required. Just remember: use the PHP file name as the template identifier, not the template name.