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□ 主题： [转] SQL删除重复数据只保留一条

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      用SQL语句,删除掉重复项只保留一条


      在几千条记录里,存在着些相同的记录,如何能用SQL语句,删除掉重复的呢
      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 peopleName in (select peopleName from people group by peopleName having count(peopleName) > 1)
      and peopleId not in (select min(peopleId) from people group by peopleName having count(peopleName)>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)

      6.消除一个字段的左边的第一位：

      update tableName set [Title]=Right([Title],(len([Title])-1)) where Title like ''村%''

      7.消除一个字段的右边的第一位：

      update tableName set [Title]=left([Title],(len([Title])-1)) where Title like ''%村''

      8.假删除表中多余的重复记录（多个字段），不包含rowid最小的记录
      update vitae set ispass=-1
      where peopleId in (select peopleId from vitae group by peopleId

——

□ 争分夺秒背单词 → gang n.一帮，一伙

□ 发帖时间：2013-11-8｜19:13:36

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