mysql(slow-query)快速开启慢日志查询的方法_MySQL
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mysql(slow-query)快速开启慢日志查询的方法
mysql有一个功能就是可以log下来运行的比较慢的sql语句，默认是没有这个log的
打开 my.ini ,找到 [mysql] 在其下面添加
long_query_time = 2
log-slow-queries = D:/mysql/logs/slow.log #设置把日志写在那里，可以为空，系统会给
一个缺省的文件
#log-slow-queries = /var/youpath/slow.log linux下host_name-slow.log
log-queries-not-using-indexes
long_query_time 是指执行超过多长时间（单位是秒）的sql会被记录下来，这里设置的是2秒。
log-slow-queries 设置日志所在位置，可以为空，系统会给一个缺省的文件
host_name-slow.log，生成的日志就在mysql的data目录下
log-queries-not-using-indexes 就是字面意思，记录下没有使用索引的query。
以下是mysqldumpslow常用参数说明，详细的可应用mysqldumpslow -help查询。
-s，是表示按照何种方式排序，c、t、l、r分别是按照记录次数、时间、查询时间、返回的
记录数来排序（从大到小），ac、at、al、ar表示相应的倒叙。
-t，是top n的意思，即为返回前面多少条数据。
-g，后边可以写一个正则匹配模式，大小写不敏感。
接下来就是用mysql自带的慢查询工具mysqldumpslow分析了（mysql的bin目录下
），我这里的日志文件名字是host-slow.log。
列出记录次数最多的10个sql语句
mysqldumpslow -s c -t 10 host-slow.log
列出返回记录集最多的10个sql语句
mysqldumpslow -s r -t 10 host-slow.log
按照时间返回前10条里面含有左连接的sql语句
mysqldumpslow -s t -t 10 -g "left join" host-slow.log
使用mysqldumpslow命令可以非常明确的得到各种我们需要的查询语句，对MySQL查
询语句的监控、分析、优化起到非常大的帮助。
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