數據庫操作中，經常會因為導數據造成數據重復，需要進行數據清理，去掉冗余的數據，只保留正確的數據

一：重復數據根據單個字段進行判斷

1、首先，查詢表中多余的數據，由關鍵字段（name）來查詢。

select * from table_name where name in (select name from table_name group by name having count(name)>1)

2、刪除表中重復數據，重復數據是根據單個字段（name）來判斷，只留有rowid最小的記錄

delete from table_name where (name) in

(select Name from table_name group by name having count(name ) >1)

and rowid not in (select min(rowid) from OA_ADDRESS_BOOK group by Name having count(name )>1)

二：重復數據根據多個字段進行判斷

1、首先，查詢表中重復數據，由關鍵字段（name ,UNIT_ID）來查詢。

select * from table_name t1 where (t1.name,t1.unit_id) in
(select t2.name,t2.unit_id from table_name t2 group by t2.name,t2.unit_id having count(*)>1)

2、刪除表中重復數據，重復數據是根據多個字段（name,UNIT_ID）來判斷，只留有rowid最小的記錄

delete from table_name a where (a.name,a.UNIT_ID) in
(select name,UNIT_ID from table_name group by name,UNIT_ID having count(*) > 1)
and rowid not in (select min(rowid) from table_name group by name,UNIT_ID having count(*)>1)

3、查詢表中重復數據，重復數據是根據多個字段（name,UNIT_ID）來判斷，不包含rowid最小的記錄

select name,unit_id from table_name a where (a.Name,a.UNIT_ID) in
(select Name,UNIT_ID from table_name group by name,UNIT_ID having count(*) > 1)
and rowid not in (select min(rowid) from table_name group by Name,UNIT_ID having count(*)>1)

Oracle刪除重復數據並且只留其中一條數據