ORACLE查詢、刪除數據庫重複記錄

假設我們有一個mytable表，且該表id字段有重複值，需要僅保留重複記錄中的一條記錄即可

• 通過rowid（根據max或min函數判斷當前表某些字段重複但rowid不重複的記錄）

--查詢
select * from mytable a where a.rowid != (select max(rowid) from mytable b where b.id = a.id);

--刪除
delete from mytable a where a.rowid != (select max(rowid) from mytable b where b.id = a.id);

• 通過group by（根據group by和having判斷重複字段並通過max函數取rowid）

--查詢
select * from mytable a group by a.id having count(a.id) > 1 order by a.id;

--刪除
delete from mytable a where rowid in (select max(rowid) from mytable b group by b.id having count(b.id) > 1);