zoukankan      html  css  js  c++  java
  • sql 删除重复记录

    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?谢谢!
    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 peopleId  in (select  peopleId  from people  group  by  peopleId  having  count(peopleId) > 1)
    and rowid not in (select min(rowid) 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)

    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
  • 相关阅读:
    分布式文件系统--->fastDFS
    varnish4.0缓存代理配置
    varnish4.0缓存代理配置
    varnish4.0缓存代理配置
    SDN 是什么
    SDN 是什么
    SDN 是什么
    Solidworks如何保存为网页可以浏览的3D格式
    github 的 配置SSH
    当一个实例被创建,__init__()就会被自动调用
  • 原文地址:https://www.cnblogs.com/liufei88866/p/2110813.html
Copyright © 2011-2022 走看看