筆記：Oracle查詢重復數據並刪除，只保留一條記錄

1、查找表中多余的重復記錄，重復記錄是根據單個字段（Id）來判斷

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

 

2、刪除表中多余的重復記錄，重復記錄是根據單個字段（Id）來判斷，只留有rowid最小的記錄

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

注意：AND后面的句子獲取到的是除去擁有rowid最小的所有的記錄（單個不重復記錄也包含），Where 與 AND之間是獲取所有含有重復記錄的字段。

 

3、查找表中多余的重復記錄（多個字段）

select * from 表 a where (a.Id,a.seq) in(select Id,seq from 表 group by Id,seq having count(*) > 1)

 

4、刪除表中多余的重復記錄（多個字段），只留有rowid最小的記錄（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、查找表中多余的重復記錄（多個字段），不包含rowid最小的記錄

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)