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  • SQL查找 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
    
    -- 更新时间 某日期以后随机
    select dateadd(ss,	abs(checksum(newid()) % 31449600),'2014-01-01 ' + CONVERT (VARCHAR, getdate(), 14))

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  • 原文地址:https://www.cnblogs.com/smartsmile/p/6234260.html
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