mysql优化 慢查询_一)_mysql慢查询优化面试题

log_slow_queries? off? 表示"慢查询"是"关闭的状态"

slow_queries_log? off? 表示慢查询日志开关是关着的

使用命令：set global log_slow_queries=on;? 这样就开启了慢查询的功能,此参数打开了,slow_query_log就自动变成了on,关闭了的话也跟着关闭.

如果thread create的时间超过了这个值,这变量slow_launch_time的值加1.

set global log_launch_time=1? 这里的时间值必须是整数,否则的话就话执行出错

慢查询的查询阀值是long_query_time 默认是10秒

要真正修改慢查询得去修改mysql的文件,内容添加如下

并且还得重新启动mysql才会生效

慢查询的日志结构如下：

MySQLa, Version: ⑤⑤40-log (MySQL Community Server (GPL)). started with:
TCP Port: 3306, Named Pipe: (null)
Time                 Id Command    Argument
# Time: 150705 18:31:54
# User@Host: root[root] @ localhost [12⑦0.0.1]
# Query_time: 0.012001  Lock_time: 0.001000 Rows_sent: 51  Rows_examined: 51
use weixin;
SET timestamp=1436092314;
show databases;
# Time: 150705 18:32:55
# User@Host: root[root] @ localhost [12⑦0.0.1]
# Query_time: 0.002000  Lock_time: 0.001000 Rows_sent: 1  Rows_examined: 1
SET timestamp=1436092375;
show variables like  "%query_time%";
# Time: 150705 18:33:03
# User@Host: root[root] @ localhost [12⑦0.0.1]
# Query_time: 0.001000  Lock_time: 0.000000 Rows_sent: 0  Rows_examined: 0
use chlitina;
SET timestamp=1436092383;
use ◆chlitina◆;
# User@Host: root[root] @ localhost [12⑦0.0.1]
# Query_time: 0.031001  Lock_time: 0.001000 Rows_sent: 869  Rows_examined: 869
SET timestamp=1436092383;
select * from wp_consultant;
# Time: 150705 18:33:40
# User@Host: root[root] @ localhost [12⑦0.0.1]
# Query_time: 0.052003  Lock_time: 0.001000 Rows_sent: 869  Rows_examined: 1738
SET timestamp=1436092420;
select * from wp_consultant order by id desc;

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