mysql导数据库用到的语句

将字段格式为2013-08-09 13:22:55转换为时间戳

UPDATE `AttendClass` SET `regdate` = unix_timestamp(regDate2) WHERE `rowid` = 118280;

将字段name前面添加一个字符x

update aa set name=concat('x',name)

MYSQL查询重复记录的方法

1、查找表中多余的重复记录，重复记录是根据单个字段（peopleId）来判断

select * from people   where peopleId in (select peopleId from people group by peopleId having count(peopleId) > 1) 

 2、删除表中多余的重复记录，重复记录是根据单个字段（peopleId）来判断，只留有rowid最小的记录

delete from people   
where peopleId in (select peopleId from people group by peopleId   having count(peopleId) > 1)   
and rowid not in (select min(rowid) from people group by peopleId having count(peopleId )>1)

 3、查找表中多余的重复记录（多个字段）

select * from vitae a   
where (a.peopleId,a.seq) in (select peopleId,seq from vitae group by peopleId,seq having count(*) > 1)

 4、删除表中多余的重复记录（多个字段），只留有rowid最小的记录

delete from vitae a   
where (a.peopleId,a.seq) in (select peopleId,seq from vitae group by peopleId,seq having count(*) > 1)   
and rowid not in (select min(rowid) from vitae group by peopleId,seq having count(*)>1)

 5、查找表中多余的重复记录（多个字段），不包含rowid最小的记录

select * from vitae a   
where (a.peopleId,a.seq) in (select peopleId,seq from vitae group by peopleId,seq having count(*) > 1)   
and rowid not in (select min(rowid) from vitae group by peopleId,seq having count(*)>1)