mysql> describe SELECT COUNT( m.id )
    ->  FROM mos_content AS i
    ->  LEFT JOIN mos_sections AS s ON i.sectionid=s.id
    ->  LEFT JOIN mos_menu AS m ON m.componentid=s.id
    ->  WHERE m.type='content_blog_section'
    ->  AND m.published='1';
+----+-------------+-------+-------+-----------------------------------------+-------------+---------+--------------------------+-------+-------------+
| id | select_type | table | type  | possible_keys                           | key         | key_len | ref                      | rows  | Extra       |
+----+-------------+-------+-------+-----------------------------------------+-------------+---------+--------------------------+-------+-------------+
|  1 | SIMPLE      | i     | index | NULL                                    | idx_section |       4 | NULL                     | 21461 | Using index |
|  1 | SIMPLE      | s     | ref   | PRIMARY,lento2                          | lento2      |       4 | notitrujillo.i.sectionid |     1 | Using index |
|  1 | SIMPLE      | m     | ref   | componentid,lento2,lento3,lento4,lento6 | componentid |       4 | notitrujillo.s.id        |     3 | Using where |
+----+-------------+-------+-------+-----------------------------------------+-------------+---------+--------------------------+-------+-------------+