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  • sql语句(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%'

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  • 原文地址:https://www.cnblogs.com/yzf666/p/8513578.html
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