oracle刪除重複資料保留第一筆記錄
1、查找表中多餘的重複記錄，重複記錄是根據單一欄位（ 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，重複記錄是根據單一欄位（Id）來判斷，只留有rowid最小的記錄
DELETE from 表 WHERE (id) IN ( SELECT id FROM 表 GROUP BY id HAVING COUNT(id) > 1) AND ROWID NOT IN (SELECT MIN(ROWID) FROM 表 GROUP BY id HAVING COUNT(*) > 1);
3、查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
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)
5、查找表中多餘的重複記錄（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)
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