平台 centos 5 ,mysql 5.1
添加在 [mysqld]后面
long_query_time = 0.01
#long_query_time = 1
slow_query_log=1
slow_query_log_file = /var/log/mysql/slow.log
#下面这个写法是没有效果的 在mysql 5.1之后
#log-slow-queries= /tmp/slowquery.log
and then restart mysqld
#注意 slow log 目录 mysqld 用户要有读写权限才行
SELECT t.TABLE_SCHEMA AS `db`,
t.TABLE_NAME AS `table`,
s.INDEX_NAME AS `index name`,
s.COLUMN_NAME AS `FIELD name`,
s.SEQ_IN_INDEX `seq IN index`,
s2.max_columns AS `# cols`,
s.CARDINALITY AS `card`,
t.TABLE_ROWS AS `est rows`,
ROUND(((s.CARDINALITY / IFNULL(t.TABLE_ROWS, 0.01)) * 100), 2) AS `sel %`
FROM INFORMATION_SCHEMA.STATISTICS s
INNER JOIN INFORMATION_SCHEMA.TABLES t ON s.TABLE_SCHEMA = t.TABLE_SCHEMA AND s.TABLE_NAME = t.TABLE_NAME
INNER JOIN (
SELECT TABLE_SCHEMA, TABLE_NAME, INDEX_NAME, MAX(SEQ_IN_INDEX) AS max_columns
FROM INFORMATION_SCHEMA.STATISTICS
WHERE TABLE_SCHEMA != 'mysql' GROUP BY TABLE_SCHEMA, TABLE_NAME, INDEX_NAME ) AS s2 ON s.TABLE_SCHEMA = s2.TABLE_SCHEMA AND s.TABLE_NAME = s2.TABLE_NAME AND s.INDEX_NAME = s2.INDEX_NAME
WHERE t.TABLE_SCHEMA != 'mysql' /* Filter out the mysql system DB */
AND t.TABLE_ROWS > 10 /* Only tables with some rows */
AND s.CARDINALITY IS NOT NULL /* Need at least one non-NULL value in the field */
AND (s.CARDINALITY / IFNULL(t.TABLE_ROWS, 0.01)) < 1.00 /* unique indexes are perfect anyway */
ORDER BY `sel %`, s.TABLE_SCHEMA, s.TABLE_NAME /* DESC for best non-unique indexes */
LIMIT 10;
#查看
tail -f /var/log/mysql/slow.log
MySQL慢查询查找和调优测试
http://www.jb51.net/article/32956.htm
