mysql> explain SELECT post_title,group_concat(cat_name) FROM wp_posts p LEFT JOIN wp_post2cat pc ON (p.ID=pc.post_id) JOIN wp_categories c ON (pc.category_id=c.cat_id)  WHERE 1=1 AND (post_type = 'post' AND (post_status = 'publish')) GROUP BY post_date DESC,ID DESC LIMIT 0, 10;
+----+-------------+-------+--------+---------------+---------+---------+--------------------------+------+--------------------------+
| id | select_type | table | type   | possible_keys | key     | key_len | ref                      | rows | Extra                    |
+----+-------------+-------+--------+---------------+---------+---------+--------------------------+------+--------------------------+
| 1  | SIMPLE      | p     | ref    | PRIMARY,blah2 | blah2   | 103     | const,const              | 1    | Using where              |
| 1  | SIMPLE      | pc    | ref    | post_id       | post_id | 8       | wordpress.p.ID           | 2    | Using where; Using index |
| 1  | SIMPLE      | c     | eq_ref | PRIMARY       | PRIMARY | 8       | wordpress.pc.category_id | 1    |                          |
+----+-------------+-------+--------+---------------+---------+---------+--------------------------+------+--------------------------+
3 rows in set (0.00 sec)