MySQL SQL优化方法是什么

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slowlog里查到一条sql执行了10秒钟以上

1. # Time: 2017-03-02T18:41:50.201376+08:00
   

2. # User@Host: oms_readonly[oms_readonly] @ [10.xx.xx.xx] Id: 54124620
   

3. # Query_time: 11.005894 Lock_time: 0.000223 Rows_sent: 20 Rows_examined: 1838114
   

4. SET timestamp=1488451310;
   

5. 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

1. 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;
   

2. +----+-------------+-----------+------------+-------+-----------------------------------------------------------------+-------+---------+------+------+----------+-------------+
   

3. | id | select_type | table | partitions | type | possible_keys | key | key_len | ref | rows | filtered | Extra |
   

4. +----+-------------+-----------+------------+-------+-----------------------------------------------------------------+-------+---------+------+------+----------+-------------+
   

5. | 1 | SIMPLE | customers | NULL | index | type,into_time,isarea,status,idx_isarea_renew_owner,type_status | score | 2 | NULL | 603 | 0.21 | Using where |
   

6. +----+-------------+-----------+------------+-------+-----------------------------------------------------------------+-------+---------+------+------+----------+-------------+
   

7. 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

1. mysql> select count(*) from customers where `type` = 1;
   

2. +----------+
   

3. | count(*) |
   

4. +----------+
   

5. | 2373175 |
   

6. +----------+
   

7. 1 row in set (1.53 sec)
   

8. 
   

9. mysql> select count(*) from customers where `status` < 7;

10.     -> ;
    

11. +----------+
    

12. | count(*) |
    

13. +----------+
    

14. | 2494232 |
    

15. +----------+
    

16. 1 row in set (3.16 sec)
    

17. 
    

18. mysql> select count(*) from customers where `isarea` = 6;

19. +----------+
    

20. | count(*) |
    

21. +----------+
    

22. | 135347 |
    

23. +----------+
    

24. 1 row in set (0.15 sec)
    

25. 
    

26. mysql> select count(*) from customers where `into_time`>='2016-12-01'AND `into_time`<='2017-01-02 23:59:59';

27. +----------+
    

28. | count(*) |
    

29. +----------+
    

30. | 106158 |
    

31. +----------+
    

32. 1 row in set (0.12 sec)

isarea有索引，强制用这个列的索引

1. 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;
   

2. +----+-------------+-----------+------------+------+---------------+--------+---------+-------+--------+----------+----------------------------------------------------+
   

3. | id | select_type | table | partitions | type | possible_keys | key | key_len | ref | rows | filtered | Extra |
   

4. +----+-------------+-----------+------------+------+---------------+--------+---------+-------+--------+----------+----------------------------------------------------+
   

5. | 1 | SIMPLE | customers | NULL | ref | isarea | isarea | 5 | const | 249438 | 1.85 | Using index condition; Using where; Using filesort |
   

6. +----+-------------+-----------+------------+------+---------------+--------+---------+-------+--------+----------+----------------------------------------------------+
   

7. 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。这里是亿速云，小编将为大家推送更多相关知识点的文章，欢迎关注！