MySQL SQL優化方法是什么

這篇文章主要講解了“MySQL SQL優化方法是什么”，文中的講解內容簡單清晰，易于學習與理解，下面請大家跟著小編的思路慢慢深入，一起來研究和學習“MySQL SQL優化方法是什么”吧！

slowlog里查到一條sql執行了10秒鐘以上

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;

查看執行計劃

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)

看下列的選擇性，很明顯isarea列的選擇性更好

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，強制用這個列的索引

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)

優化前10幾秒出結果，優化后0.5秒出結果。

感謝各位的閱讀，以上就是“MySQL SQL優化方法是什么”的內容了，經過本文的學習后，相信大家對MySQL SQL優化方法是什么這一問題有了更深刻的體會，具體使用情況還需要大家實踐驗證。這里是億速云，小編將為大家推送更多相關知識點的文章，歡迎關注！