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  • MySQL查询及删除重复记录的方法

    查询及删除重复记录的方法
    (一)
    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,只留有一个记录
    delete from people
    where peopleId in (select peopleId from people group by peopleId having count(peopleId) > 1)
    and min(id) not in (select id from people group by peopleId having count(peopleId )>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)

    (二)
    比方说
    在A表中存在一个字段“name”,
    而且不同记录之间的“name”值有可能会相同,
    现在就是需要查询出在该表中的各记录之间,“name”值存在重复的项;
    Select Name,Count(*) From A Group By Name Having Count(*) > 1

    如果还查性别也相同大则如下:
    Select Name,sex,Count(*) From A Group By Name,sex Having Count(*) > 1

    (三)
    方法一

    declare @max integer,@id integer

    declare cur_rows cursor local for select 主字段,count(*) from 表名 group by 主字段 having count(*) >; 1

    open cur_rows

    fetch cur_rows into @id,@max

    while @@fetch_status=0

    begin

    select @max = @max -1

    set rowcount @max

    delete from 表名 where 主字段 = @id

    fetch cur_rows into @id,@max

    end

    close cur_rows

    set rowcount 0

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  • 原文地址:https://www.cnblogs.com/interdrp/p/5841121.html
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