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    SQL如何删除重复数据

    醉折花枝作酒筹醉折花枝作酒筹2021-05-11 17:10:48原创6242

    在sql中,可以使用select语句删除重复数据,语法为:“select * from 字段 where 字段id in (select 字段id from 字段 group by 字段 having count(字段id) > 1)”。

    本教程操作环境:windows7系统、mysql8.0版本、Dell G3电脑。

    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

    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)

    扩展:

    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)

    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)

    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)

    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)

    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%'

    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'

    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=-1where peopleId in (select peopleId from vitae group by peopleId

    相关推荐:《mysql教程

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