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)

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