• SQL删除重复数据只保留一条


     

     

     
    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

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  • 原文地址:https://www.cnblogs.com/taomylife/p/3522422.html
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