select documents.* from `xe_documents` as documents,`xe_modules` as modules   where (modules.module = 'board' and documents.module_srl = modules.module_srl) order by documents.list_order asc limit 21;

요놈이 새로 등극~


explain select documents.* from `xe_documents` as documents,`xe_modules` as modules   where (modules.module = 'board' and documents.module_srl = modules.module_srl) order by documents.list_order asc limit 9;
+----+-------------+-----------+------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+----------------+---------+---------------------------+------+----------------------------------------------+
| id | select_type | table     | type | possible_keys                                                                                                                                                                                  | key            | key_len | ref                       | rows | Extra                                        |
+----+-------------+-----------+------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+----------------+---------+---------------------------+------+----------------------------------------------+
|  1 | SIMPLE      | modules   | ref  | PRIMARY,idx_module                                                                                                                                                                             | idx_module     | 242     | const                     |  394 | Using where; Using temporary; Using filesort |
|  1 | SIMPLE      | documents | ref  | idx_module_srl,idx_module_list_order,idx_module_update_order,idx_module_readed_count,idx_module_voted_count,idx_module_notice,idx_module_document_srl,idx_module_blamed_count,idx_reward_point | idx_module_srl | 8       | test4u.modules.module_srl |   27 |