SQL Join Sum表不同於單個查詢

Question

我的問題是：我有3個表Invoiced ， Expired ， Payed ，每個表都有這些列：

• customer_code
• 類型
• 量

在Oracle中，我試圖這樣做：

SELECT
    C.customer_code,
    C.type,
    SUM(C.AMOUNT)  AS AMOUNT_EXPIRED,
    SUM(F.AMOUNT)  AS AMOUNT_INVOICED,
    SUM(R.AMOUNT)  AS AMOUNT_PAYED        
  FROM Expired C
  LEFT JOIN (SELECT customer_code, ACCOUNT, SUM(AMOUNT) AS AMOUNT
               FROM Invoiced
              GROUP BY customer_code, type) F
    ON C.customer_code = F.customer_code
   AND C.type = F.type
LEFT JOIN (SELECT customer_code, type, SUM(AMOUNT) AS AMOUNT
             FROM Payed
            GROUP BY customer_code, type) R
    ON C.customer_code = R.customer_code
   AND C.type = R.type
 GROUP BY C.customer_code, C.type,
          R.customer_code, R.type, 
          F.customer_code, F.type

我得到一個帶有列的表：

------------------------------------------------------------------------
 customer_code | type | amount_expired | amount invoiced | amount payed
------------------------------------------------------------------------ 

但是對於單個查詢，金額是不同的：

SELECT customer_code, type, SUM(AMOUNT) AS AMOUNT FROM expired GROUP BY customer_code, type
SELECT customer_code, type, SUM(AMOUNT) AS AMOUNT FROM invoiced GROUP BY customer_code, type
SELECT customer_code, type, SUM(AMOUNT) AS AMOUNT FROM payed GROUP BY customer_code, type

有人可以幫助我嗎？

Answer 1

使用union而不是join 。 但是，您應該有一個表來存儲所有客戶代碼和類型。 而且，在涉及聚合函數時，永遠不要使用join 。 這非常令人困惑，通常會產生不正確的結果。

with CUSTOMER as (
    select CUSTOMER_CODE, TYPE from EXPIRED group by CUSTOMER_CODE, TYPE
    union 
    select CUSTOMER_CODE, TYPE from INVOICED group by CUSTOMER_CODE, TYPE
    union 
    select CUSTOMER_CODE, TYPE from PAYED group by CUSTOMER_CODE, TYPE
)
select
    c.CUSTOMER_CODE, c.TYPE
    ,(
    select sum(AMOUNT) 
    from EXPIRED 
    where CUSTOMER_CODE = c.CUSTOMER_CODE and TYPE = c.TYPE
    ) as AMOUNT_EXPIRED
    ,(
    select sum(AMOUNT) 
    from INVOICED 
    where CUSTOMER_CODE = c.CUSTOMER_CODE and TYPE = c.TYPE
    ) as AMOUNT_INVOICED
    ,(
    select sum(AMOUNT) 
    from PAYED 
    where CUSTOMER_CODE = c.CUSTOMER_CODE and TYPE = c.TYPE
    ) as AMOUNT_EXPIRED
from CUSTOMER c
order by c.CUSTOMER_CODE, c.TYPE

Answer 2

您的第二個子查詢可能是原因，這可能是您期望的；

SELECT  C.customer_code, C.type, 
    SUM(C.AMOUNT)       AS AMOUNT_EXPIRED,
    SUM(F.AMOUNT)       AS AMOUNT_INVOICED,
    SUM(R.AMOUNT)       AS AMOUNT_PAYED        
FROM      Expired C
LEFT JOIN invoiced F
ON        C.customer_code= F.customer_code
AND       C.type= F.type
LEFT JOIN payed R 
ON        C.customer_code= R.customer_code
AND       C.type= R.type

GROUP BY  C.customer_code, C.type