GLOBAL variable and should be set with SET GLOBAL

方法1，用命令开启慢查询

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1.mysql> show variables like "%long%"; //查看一下默认为慢查询的时间10秒
2.+-----------------+-----------+
3.| Variable_name | Value |
4.+-----------------+-----------+
5.| long_query_time | 10.000000 |
6.+-----------------+-----------+
7.1 row in set (0.00 sec)
8.
9.mysql> set global long_query_time=2; //设置成2秒，加上global,下次进mysql已然生效
10.Query OK, 0 rows affected (0.00 sec)
11.
12.mysql> show variables like "%slow%"; //查看一下慢查询是不是已经开启
13.+---------------------+---------------------------------+
14.| Variable_name | Value |
15.+---------------------+---------------------------------+
16.| log_slow_queries | OFF |
17.| slow_launch_time | 2 |
18.| slow_query_log | OFF |
19.| slow_query_log_file | /usr/local/mysql/mysql-slow.log |
20.+---------------------+---------------------------------+
21.4 rows in set (0.00 sec)

22.set character_set_results=utf8;

23.mysql> set slow_query_log='ON'; //加上global，不然会报错的。
24.ERROR 1229 (HY000): Variable 'slow_query_log' is a GLOBAL variable and should be set with SET GLOBAL
25.mysql> set global slow_query_log='ON'; //启用慢查询
26.Query OK, 0 rows affected (0.28 sec)
27.
28.mysql> show variables like "%slow%"; //查看是否已经开启
29.+---------------------+---------------------------------+
30.| Variable_name | Value |
31.+---------------------+---------------------------------+
32.| log_slow_queries | ON |
33.| slow_launch_time | 2 |
34.| slow_query_log | ON |
35.| slow_query_log_file | /usr/local/mysql/mysql-slow.log |
36.+---------------------+---------------------------------+
37.4 rows in set (0.00 sec)
mysql> show variables like "%long%"; //查看一下默认为慢查询的时间10秒
+-----------------+-----------+
| Variable_name | Value |
+-----------------+-----------+
| long_query_time | 10.000000 |
+-----------------+-----------+
1 row in set (0.00 sec)

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)

mysql> show variables like "%slow%"; //查看一下慢查询是不是已经开启
+---------------------+---------------------------------+
| Variable_name | Value |
+---------------------+---------------------------------+
| log_slow_queries | OFF |
| slow_launch_time | 2 |
| slow_query_log | OFF |
| slow_query_log_file | /usr/local/mysql/mysql-slow.log |
+---------------------+---------------------------------+
4 rows in set (0.00 sec)

mysql> set slow_query_log='ON'; //加上global，不然会报错的。
ERROR 1229 (HY000): Variable 'slow_query_log' is a GLOBAL variable and should be set with SET GLOBAL
mysql> set global slow_query_log='ON'; //启用慢查询
Query OK, 0 rows affected (0.28 sec)

mysql> show variables like "%slow%"; //查看是否已经开启
+---------------------+---------------------------------+
| Variable_name | Value |
+---------------------+---------------------------------+
| log_slow_queries | ON |
| slow_launch_time | 2 |
| slow_query_log | ON |
| slow_query_log_file | /usr/local/mysql/mysql-slow.log |
+---------------------+---------------------------------+
4 rows in set (0.00 sec)