linux下开启mysql慢查询，分析查询语句

启用MySQL慢查询

一，到配置文件里面添加代码

1. 
   
2. vim /etc/my.cnf
3. [mysqld]
4. slow-query-log = on # 开启慢查询功能
5. slow_query_log_file = /usr/local/mysql/data/slow-query.log # 慢查询日志存放路径与名称
6. long_query_time = 5 # 查询时间超过5s的查询语句
7. ### log-queries-not-using-indexes = on # 列出没有使用索引的查询语句

二，，用命令开启慢查询

1. 
   
2. mysql> show variables like "%long%"; //查看一下默认为慢查询的时间10秒
3. +-----------------+-----------+
4. | Variable_name | Value |
5. +-----------------+-----------+
6. | long_query_time | 10.000000 |
7. +-----------------+-----------+
8. 1 row in set (0.00 sec)
10. mysql> set global long_query_time=2; //设置成2秒，加上global,下次进mysql已然生效 Query OK, 0 rows affected (0.00 sec)
11. mysql> show variables like "%slow%"; //查看一下慢查询是不是已经开启
12. +---------------------+---------------------------------+
13. | Variable_name | Value |
14. +---------------------+---------------------------------+
15. | log_slow_queries | OFF |
16. | slow_launch_time | 2 |
17. | slow_query_log | OFF |
18. | slow_query_log_file | /usr/local/mysql/mysql-slow.log |
19. +---------------------+---------------------------------+
20. 4 rows in set (0.00 sec)
22. mysql> set slow_query_log='ON'; //加上global，不然会报错的。
23. ERROR 1229 (HY000): Variable 'slow_query_log' is a GLOBAL variable and should be set with SET GLOBAL
24. mysql> set global slow_query_log='ON'; //启用慢查询
25. Query OK, 0 rows affected (0.28 sec)
27. mysql> show variables like "%slow%"; //查看是否已经开启
28. +---------------------+---------------------------------+
29. | Variable_name | Value |
30. +---------------------+---------------------------------+
31. | log_slow_queries | ON |
32. | slow_launch_time | 2 |
33. | slow_query_log | ON |
34. | slow_query_log_file | /usr/local/mysql/mysql-slow.log |
35. +---------------------+---------------------------------+
36. 4 rows in set (0.00 sec)