無法更新視圖或函數'cte'，因爲它包含集合，或者DISTINCT或GROUP BY子句，或者PIVOT或UNPIVOT運算符

Question

我想要使用Having by來刪除。

所以我儘量執行以下語句：

;WITH cte As 
(
select emp_num, [from_date],[to_date],[ req_ser], [ req_year] 
from empmission 
group by emp_num, [from_date],[to_date],[ req_ser], [ req_year] 
having count(*) >2 
) 

DELETE 
FROM cte 

，但我得到以下異常：

無法更新視圖或函數「CTE」，因爲它包含 聚集，或DISTINCT或GROUP BY子句，或者PIVOT或UNPIVOT運算符。

Answer 1

使用窗口功能：

WITH todelete As (
     select em.*, 
      row_number() over (partition by emp_num, [from_date],[to_date],[ req_ser], [ req_year] 
           order by (select null)) as cnt 
     from empmission em 
) 

DELETE FROM todelete 
WHERE cnt > 2; 

注意，這將刪除所有行有重複的值。通常情況下，你想保留其中的一個值。如果是這樣，請提出另一個問題。

Answer 2

內部連接回到原始表並刪除它。

;WITH cte As 
(
select emp_num, [from_date],[to_date],[ req_ser], [ req_year] 
from  empmission 
group by emp_num, [from_date],[to_date],[ req_ser], [ req_year] 
having count(*) >2 
)  
DELETE E 
FROM cte C 
JOIN empmission E ON C.emp_num = E.emp_num 
         AND C.from_date = E.from_date 
         AND C.to_date = E.to_date 
         AND C.req_ser = E.req_ser 
         AND C.req_year = E.req_year 

Answer 3

的另一種方式，跳過CTE，做EXISTS代替：

delete from empmission e1 
where exists (select 1 
       from empmission e2 
       where e1.emp_num = e1.emp_num 
       and e1.[from_date] = e2.[from_date] 
       and e1.[to_date] = e2.[to_date] 
       and e1.[ req_ser] = e2.[ req_ser] 
       and e1.[ req_year] = e2.[ req_year] 
       group by emp_num, [from_date],[to_date],[ req_ser], [ req_year] 
       having count(*) > 2)