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  • SQL删除重复数据只保留一条

    一、查询全部的重复数据

      select * from CHECKINOUT  where userid  in (select USERID from CHECKINOUT GROUP by USERID,checktime HAVING count(*)>1
    ) and checktime    in (select checktime from CHECKINOUT group by USERID,checktime having count(*) > 1)

    二、删除重复数据保留一条记录

     1、首先在表中新增一列自动增长列

          Alter Table CHECKINOUT  Add ID int Identity(1,1)

     2、在删除重复数据保留一条记录

      Delete from CHECKINOUT  Where ID Not In (
      Select MIN(ID) From CHECKINOUT  Group by USERID,CHECKTIME )

    3、最后再在表中删除新建的自动增长列

    4、

    select PropertyNo from pro_propertys
    where isdelete=0 and propertyno in
    (
    select propertyno From pro_propertys
    where isdelete=0
    group by propertyno
    having count(1)>1
    )

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  • 原文地址:https://www.cnblogs.com/starts/p/5258830.html
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