linux下開啓mysql慢查詢，分析查詢語句

啓用MySQL慢查詢

一，到配置文件裏面添加代碼

vim /etc/my.cnf
[mysqld]
slow-query-log = on # 開啓慢查詢功能
slow_query_log_file = /usr/local/mysql/data/slow-query.log # 慢查詢日誌存放路徑與名稱
long_query_time = 5 # 查詢時間超過5s的查詢語句
### log-queries-not-using-indexes = on # 列出沒有使用索引的查詢語句

二，，用命令開啓慢查詢

mysql> show variables like "%long%";         //查看一下默認爲慢查詢的時間10秒  
+-----------------+-----------+  
| Variable_name   | Value     |  
+-----------------+-----------+  
| long_query_time | 10.000000 |  
+-----------------+-----------+  
1 row in set (0.00 sec)  
  
mysql> set global long_query_time=2;          //設置成2秒，加上global,下次進mysql已然生效  Query OK, 0 rows affected (0.00 sec)  
  mysql> show variables like "%slow%";          //查看一下慢查詢是不是已經開啓  
+---------------------+---------------------------------+  
| 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，不然會報錯的。  
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';            //啓用慢查詢  
Query OK, 0 rows affected (0.28 sec)  
  
mysql> show variables like "%slow%";              //查看是否已經開啓  
+---------------------+---------------------------------+  
| 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)