oracle 查詢重複數據並且刪除, 只保留一條數據

數據庫操作中，經常會因爲導數據造成數據重複，需要進行數據清理，去掉冗餘的數據，只保留正確的數據

一：重複數據根據單個字段進行判斷

1、首先，查詢表中多餘的數據，由關鍵字段（name）來查詢。

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

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

delete from OA_ADDRESS_BOOK where (Name) in 

(select Name from OA_ADDRESS_BOOK 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：重複數據根據多個字段進行判斷

1、首先，查詢表中重複數據，由關鍵字段（Name,UNIT_ID）來查詢。

select * from OA_ADDRESS_BOOK book1 where (book1.name,book1.unit_id) in 
(select book2.name,book2.unit_id from OA_ADDRESS_BOOK book2 group by  book2.name,book2.unit_id  having count(*)>1)

2、刪除表中重複數據，重複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 OA_ADDRESS_BOOK a where (a.Name,a.UNIT_ID) in 
(select Name,UNIT_ID from OA_ADDRESS_BOOK group by Name,UNIT_ID having count(*) > 1) 
and rowid not in (select min(rowid) from OA_ADDRESS_BOOK group by Name,UNIT_ID having count(*)>1)

3、查詢表中重複數據，重複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 OA_ADDRESS_BOOK a where (a.Name,a.UNIT_ID) in 
(select Name,UNIT_ID from OA_ADDRESS_BOOK group by Name,UNIT_ID having count(*) > 1) 
and rowid not in (select min(rowid) from OA_ADDRESS_BOOK group by Name,UNIT_ID having count(*)>1)