筆記：Oracle查詢重複資料並刪除，只保留一條記錄

標籤：保留   刪除表   尋找   from   刪除   不包含   span   having   sel   

1、尋找表中多餘的重複記錄，重複記錄是根據單個欄位（Id）來判斷

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

 

2、刪除表中多餘的重複記錄，重複記錄是根據單個欄位（Id）來判斷，只留有rowid最小的記錄

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

注意：AND後面的句子擷取到的是除去擁有rowid最小的所有的記錄（單個不重複記錄也包含），Where 與 AND之間是擷取所有含有重複記錄的欄位。

 

3、尋找表中多餘的重複記錄（多個欄位）

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

 

4、刪除表中多餘的重複記錄（多個欄位），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)

樣本二：delete from student where s_id not in(select min(s_id) from student group by s_name,c_id);

 

5、尋找表中多餘的重複記錄（多個欄位），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)

 

筆記：Oracle查詢重複資料並刪除，只保留一條記錄