mysql> explain SELECT sts.template_id, image_id FROM system_templates_defaults std LEFT JOIN system_templates_images sti ON std.template_image_id = sti.temp_image_id LEFT JOIN system_templates_styles sts ON std.template_style_id = sts.template_style_id WHERE sti.template_id = sts.template_id AND sts.template_id =1 ;
+-------+--------+---------------------+---------+---------+-----------------------+------+-------------+
| table | type   | possible_keys       | key     | key_len | ref                   | rows | Extra       |
+-------+--------+---------------------+---------+---------+-----------------------+------+-------------+
| std   | ALL    | NULL                | NULL    |    NULL | NULL                  |    1 |             |
| sti   | eq_ref | PRIMARY,template_id | PRIMARY |       4 | std.template_image_id |    1 | Using where |
| sts   | eq_ref | PRIMARY,template_id | PRIMARY |       4 | std.template_style_id |    1 | Using where |
+-------+--------+---------------------+---------+---------+-----------------------+------+-------------+
3 rows in set (0.02 sec)