zoukankan      html  css  js  c++  java
  • 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,seq having count(*) > 1) and seq in (select 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)

    感谢来访,共同学习!
  • 相关阅读:
    Hibernate3 第一天
    Struts2第四天
    Struts2第二天
    Struts2第一天
    【剑指offer】数字在排序数组中出现的次数,C++实现
    【剑指offer】两个链表的第一个公共结点,C++实现
    【剑指offer】数组中的逆序对。C++实现
    [Python]定时任务框架 APScheduler
    [pandas] SettingWithCopyWarning: A value is trying to be set on a copy of a slice from a DataFrame
    alicode35-找出二叉搜索树的第2大的数
  • 原文地址:https://www.cnblogs.com/dingxiaowei/p/3058833.html
Copyright © 2011-2022 走看看