wpdb object can be used to run arbitrary queries against the WordPress database. Let's say you want to list the most recent 4 posts:
$results = $wpdb->get_results( "SELECT * FROM $wpdb->posts WHERE `post_type`='post' LIMIT 4" );
$wpdb->posts variable will output the table name for posts. It's usually
wp_posts, but if you're using a custom database prefix this could be different.
However, if you're trying to grab post data (or custom post data or meta information or user data or ... anything built-in to WordPress), you should really be using
Here's the same query above, re-written for
$query = new WP_Query(
'post_type' => 'post',
'posts_per_page' => 4
The advantage of using
WP_Query is that it will automatically join against the post meta table and return an array of
WP_Post objects that you can work with and loop through.