資料庫操作中，經常會因為導資料造成資料重複，需要進行資料清理，去掉冗餘的資料，只保留正確的資料

一：重複資料根據單個欄位進行判斷

1、首先，查詢表中多餘的資料，由關鍵欄位（name）來查詢。

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

2、刪除表中重複資料，重複資料是根據單個欄位（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：重複資料根據多個欄位進行判斷

1、首先，查詢表中重複資料，由關鍵欄位（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、刪除表中重複資料，重複資料是根據多個欄位（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、查詢表中重複資料，重複資料是根據多個欄位（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)