mysql怎么查重复数据 mysql如何查重

MySql怎么查询重复的数据

select name,sum(num) from table group by name

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--group by 分组查询可以实现，根据名称分组查询累加数量

你是要查找数据库中某个字段下的相同数据吧，我给你写2个例子

(数据库执行效率高)

select * from dbo.MediafileInfo as a where

(VideoDownUrl IN (SELECT VideoDownUrl FROM MediafileInfo AS B WHERE A.ProgramID B.ProgramID))

(数据库执行效率低)

SELECT *

FROM MediafileInfo AS A

WHERE (SELECT COUNT(*) FROM MediafileInfo WHERE VideoDownUrl=A.VideoDownUrl)1

select * from tableName where (bookname,borrowtime) in (select bookname,borrowtime from tableName group by bookname,borrowtime having count(*) 1);

select distinct biao.id

from biao

left outer join (select col1, col2

from biao

group by col1, col2

having count(*) 1) tmp

on biao.col1 = tmp.col1

and biao.col2 = tmp.col2

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