gistfile1.txt

    /**
    *Get distinct values of custom field from post type
    *
    *@return void
    *@since 0.1
    */
    function get_distinct_from_post_type ( $field, $post_type ) {
        global $wpdb;
        $sql = "SELECT DISTINCT meta_value FROM $wpdb->postmeta pm, $wpdb->posts p WHERE meta_key  = '$field' AND pm.post_id=p.ID AND p.post_type='$post_type' ORDER BY meta_value";
        return $wpdb->get_results( $sql, ARRAY_A );
    }