这篇文章主要讲解了“MySQL SQL优化方法是什么”，文中的讲解内容简单清晰，易于学习与理解，下面请大家跟着小编的思路慢慢深入，一起来研究和学习“MySQL SQL优化方法是什么”吧！
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slowlog里查到一条sql执行了10秒钟以上
# Time: 2017-03-02T18:41:50.201376+08:00
# User@Host: oms_readonly[oms_readonly] @ [10.xx.xx.xx] Id: 54124620
# Query_time: 11.005894 Lock_time: 0.000223 Rows_sent: 20 Rows_examined: 1838114
SET timestamp=1488451310;
select * from customers where `type` = 1 AND `status` < 7 AND `isarea` = 6 AND `into_time`>='2016-12-01'AND `into_time`<='2017-01-02 23:59:59' order by score desc limit 40,20;
查看执行计划
mysql> explain select * from customers where `type` = 1 AND `status` < 7 AND `isarea` = 6 AND `into_time`>='2016-12-01'AND `into_time`<='2017-01-02 23:59:59' order by score desc limit 40,20;
+----+-------------+-----------+------------+-------+-----------------------------------------------------------------+-------+---------+------+------+----------+-------------+
| id | select_type | table | partitions | type | possible_keys | key | key_len | ref | rows | filtered | Extra |
+----+-------------+-----------+------------+-------+-----------------------------------------------------------------+-------+---------+------+------+----------+-------------+
| 1 | SIMPLE | customers | NULL | index | type,into_time,isarea,status,idx_isarea_renew_owner,type_status | score | 2 | NULL | 603 | 0.21 | Using where |
+----+-------------+-----------+------------+-------+-----------------------------------------------------------------+-------+---------+------+------+----------+-------------+
1 row in set, 1 warning (0.00 sec)
看下列的选择性，很明显isarea列的选择性更好
mysql> select count(*) from customers where `type` = 1;
+----------+
| count(*) |
+----------+
| 2373175 |
+----------+
1 row in set (1.53 sec)
mysql> select count(*) from customers where `status` < 7;
-> ;
+----------+
| count(*) |
+----------+
| 2494232 |
+----------+
1 row in set (3.16 sec)
mysql> select count(*) from customers where `isarea` = 6;
+----------+
| count(*) |
+----------+
| 135347 |
+----------+
1 row in set (0.15 sec)
mysql> select count(*) from customers where `into_time`>='2016-12-01'AND `into_time`<='2017-01-02 23:59:59';
+----------+
| count(*) |
+----------+
| 106158 |
+----------+
1 row in set (0.12 sec)
isarea有索引，强制用这个列的索引
mysql> explain select * from customers use index(isarea) where `type` = 1 AND `status` < 7 AND `isarea` = 6 AND `into_time`>='2016-12-01'AND `into_time`<='2017-01-02 23:59:59' order by score desc limit 40,20;
+----+-------------+-----------+------------+------+---------------+--------+---------+-------+--------+----------+----------------------------------------------------+
| id | select_type | table | partitions | type | possible_keys | key | key_len | ref | rows | filtered | Extra |
+----+-------------+-----------+------------+------+---------------+--------+---------+-------+--------+----------+----------------------------------------------------+
| 1 | SIMPLE | customers | NULL | ref | isarea | isarea | 5 | const | 249438 | 1.85 | Using index condition; Using where; Using filesort |
+----+-------------+-----------+------------+------+---------------+--------+---------+-------+--------+----------+----------------------------------------------------+
1 row in set, 1 warning (0.00 sec)
优化前10几秒出结果，优化后0.5秒出结果。
感谢各位的阅读，以上就是“MySQL SQL优化方法是什么”的内容了，经过本文的学习后，相信大家对MySQL SQL优化方法是什么这一问题有了更深刻的体会，具体使用情况还需要大家实践验证。这里是创新互联，小编将为大家推送更多相关知识点的文章，欢迎关注！
