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 □ 主题: [转] SQL删除重复数据只保留一条
 □ 内容: 1楼

      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 → predict  v.预言,预告,预测
 □ 发帖时间:2013-11-8|19:13:36 |回复|返回|

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