EchoHi 工作日记

日志信息：

InnoDB: No valid checkpoint found.
InnoDB: If this error appears when you are creating an InnoDB database,
InnoDB: the problem may be that during an earlier attempt you managed
InnoDB: to create the InnoDB data files, but log file creation failed.
InnoDB: If that is the case, please refer to
InnoDB: http://dev.mysql.com/doc/refman/5.0/en/error-creating-innodb.html

解决办法：删除所有现有的ibdataN和ib_logfileN文件后，重启Mysql

Mysql

You can’t specify target table xxx for update in FROM clause

Mysql update、delete操作，子查询数据表不能为当前表

Mysql

SELECT c1, c2 FROM t1 GROUP BY c1, c2;
分别以c1、c2作为分组对象进行分组统计。

Mysql GROUP BY