select id,like_count,favorite_count from message_message where id in(select message_id from message_message_tags where messagetag_id=62101) and (category=9 or category=1) order by (like_count+favorite_count) desc

原因是in子句的数据量大的话，性能就会非常低下。详见：

修改成多表查询：

select t1.sender_id,t1.id,t1.like_count,t1.favorite_count,t1.add_datetime from message_message t1, message_message2tag t2 where t1.id = t2.message_id and t2.tag_id=120560 and t1.category in (9,1) and t1.add_datetime>'2012-06-29' and t1.add_datetime < '2012-07-03' order by (like_count+favorite_count) desc limit 60

性能解决了，但发现有重复记录：

+----------+------------+----------------+-----------+---------------------+

| id       | like_count | favorite_count | sender_id | add_datetime        |

+----------+------------+----------------+-----------+---------------------+

| 33850491 |          2 |            220 |    471956 | 2012-06-29 20:42:47 |

| 33778187 |         14 |            167 |    122216 | 2012-06-29 12:24:15 |

| 33779339 |          8 |            165 |    122216 | 2012-06-29 12:33:57 |

| 34068745 |          0 |            112 |      3054 | 2012-07-01 15:00:26 |

| 33782239 |          4 |             94 |    116633 | 2012-06-29 12:58:23 |

| 33815718 |          2 |             92 |      4287 | 2012-06-29 17:10:13 |

| 33905850 |          3 |             87 |     85131 | 2012-06-30 10:36:39 |

| 33827272 |          1 |             75 |    171462 | 2012-06-29 18:21:31 |

| 33778798 |          7 |             69 |    122216 | 2012-06-29 12:29:38 |

| 33780283 |          8 |             64 |    122216 | 2012-06-29 12:42:15 |

| 33816638 |          0 |             59 |      4287 | 2012-06-29 17:16:16 |

122216一个会员发了多条记录，看来需要做distinct，直接把distinct加在字段前面是没有效果，可以通过结合子查询来和group来做，最终版：

select * from (select t1.sender_id,t1.id,t1.like_count,t1.favorite_count,t1.add_datetime from message_message t1, message_message2tag t2 where t1.id = t2.message_id and t2.tag_id=120560 and t1.category in (9,1) and t1.add_datetime>'2012-06-29' and t1.add_datetime < '2012-07-03' order by (like_count+favorite_count) desc limit 60) as t group by t.sender_id order by (like_count+favorite_count) desc;

这个人提到说通过

select *, count(distinct name) from table group by name来实现

http://hi.baidu.com/liveinyc/blog/item/facac543a2dc260b9213c658.html

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2012-07-04 16:03

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分类:数据库

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