Select多行SQL语句慢查询优化-PHP Tutorial-php.cn

Select多行SQL语句慢查询优化

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Release： 2016-06-06 20:49:15

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环境：MySQL5.5 InnoDB表 post ，主键为 id

需求非常简单，根据id返回 post.name ，需要一次返回指定的多个，所以使用了where id in：

<code>select `name` from `post` where `id` in(2142324,2106574,2106564,2075699,2065402,2050790,2038346,2038345,2035588,2031765,2022035,2022034,2020745,2020737,2020718,1987558,1970241,1962232,1911342,1891481,1889641,1877438,1877434,1867217,1866057,1866013,1847315);
</code>

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Explain结果：

<code>+----+-------------+-------+-------+---------------+---------+---------+------+------+-------------+
| id | select_type | table | type  | possible_keys | key     | key_len | ref  | rows | Extra       |
+----+-------------+-------+-------+---------------+---------+---------+------+------+-------------+
|  1 | SIMPLE      | post  | range | PRIMARY       | PRIMARY | 4       | NULL |   27 | Using where |
+----+-------------+-------+-------+---------------+---------+---------+------+------+-------------+
</code>

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现在这句SQL一小时产生几千条慢查询记录，我直接在console执行每次也需要7,8秒

能怎么优化呢？

回复内容：

环境：MySQL5.5 InnoDB表 post ，主键为 id

需求非常简单，根据id返回 post.name ，需要一次返回指定的多个，所以使用了where id in：

<code>select `name` from `post` where `id` in(2142324,2106574,2106564,2075699,2065402,2050790,2038346,2038345,2035588,2031765,2022035,2022034,2020745,2020737,2020718,1987558,1970241,1962232,1911342,1891481,1889641,1877438,1877434,1867217,1866057,1866013,1847315);
</code>

Copy after login

Explain结果：

<code>+----+-------------+-------+-------+---------------+---------+---------+------+------+-------------+
| id | select_type | table | type  | possible_keys | key     | key_len | ref  | rows | Extra       |
+----+-------------+-------+-------+---------------+---------+---------+------+------+-------------+
|  1 | SIMPLE      | post  | range | PRIMARY       | PRIMARY | 4       | NULL |   27 | Using where |
+----+-------------+-------+-------+---------------+---------+---------+------+------+-------------+
</code>

Copy after login

现在这句SQL一小时产生几千条慢查询记录，我直接在console执行每次也需要7,8秒

能怎么优化呢？

从纯sql的角度看是没问题的，走了索引，rows值也不大，如果速度很慢，可以从3个方面看 1：innodb参数是否已经优化，比如innodbbufferpoor_size等 2：qcache命中率。根据你上诉问题，一小时该语句产生几千条慢查询，命中率明显不高，是否该表写入频率过高导致qcache失效，是否考虑读写分离 3：数据量大的话考虑分区，或者水平分表