zoukankan      html  css  js  c++  java
  • 笔记:Oracle查询重复数据并删除,只保留一条记录

    1、查找表中多余的重复记录,重复记录是根据单个字段(Id)来判断

    select * from 表 where Id in (select Id from 表 group byId having count(Id) > 1)

     

    2、删除表中多余的重复记录,重复记录是根据单个字段(Id)来判断,只留有rowid最小的记录

    DELETE from 表 WHERE (判断字段) IN ( SELECT 判断字段 FROM 表 GROUP BY 判断字段 HAVING COUNT(判断字段) > 1) AND ROWID NOT IN (SELECT MIN(ROWID) FROM 表 GROUP BY id HAVING COUNT(*) > 1);

    注意:AND后面的句子获取到的是除去拥有rowid最小的所有的记录(单个不重复记录也包含),Where 与 AND之间是获取所有含有重复记录的字段。

     

    3、查找表中多余的重复记录(多个字段)

    select * from 表 a where (a.Id,a.seq) in(select Id,seq from 表 group by Id,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(原理同2)

    delete from 表 a where (a.Id,a.seq) in (select Id,seq from 表 group by Id,seq having count(*) > 1) and rowid not in (select min(rowid) from 表 group by Id,seq having count(*)>1)

    示例二:delete from student where s_id not in(select min(s_id) from student group by s_name,c_id);

     

    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 表 a where (a.Id,a.seq) in (select Id,seq from 表 group by Id,seq having count(*) > 1) and rowid not in (select min(rowid) from 表 group by Id,seq having count(*)>1)

     

  • 相关阅读:
    前端git开发分支各种场景管理
    RxJS Subject学习
    微信小程序登陆流程(20200322)
    vue依赖收集的策略
    eggjs2.x版本异步获取config配置方案
    dubbo连接过程
    计算机中对流的理解
    Egg.js运行环境配置场景
    Promise和Observable的映射
    eggjs异常捕获机制
  • 原文地址:https://www.cnblogs.com/cnblog-long/p/7095923.html
Copyright © 2011-2022 走看看