SQL Case Statement NULL列

Question

proc SQL;


CREATE TABLE DATA.DUMMY AS
SELECT *,  
  CASE 
  WHEN (Discount IS NOT NULL) 
    THEN (Total_Retail_Price - (Total_Retail_Price * Discount)) * Quantity AS Rev
  ELSE (Total_Retail_Price * Quantity) AS Rev
  END

FROM DATA.Cumulative_Profit_2013 AS P

;

我正在嘗試將可能為NULL的列作為收入表達式的一部分。 但是我的案情陳述引發了問題。 我檢查了其他示例，但看不到為什么會有幫助

Answer 1

看起來您可以使用COALESCE來實現目標，而無需明確的條件：

SELECT *,  
  (Total_Retail_Price - (Total_Retail_Price * COALESCE(Discount, 0))) * Quantity AS Rev
FROM DATA.Cumulative_Profit_2013 AS P

Answer 2

在不知道SAS的情況下，正常的SQL語法為：

SELECT *,  
  CASE 
   WHEN (Discount IS NOT NULL) 
    THEN (Total_Retail_Price - (Total_Retail_Price * Discount)) * Quantity 
   ELSE (Total_Retail_Price * Quantity)
  END AS Rev

即，case表達式結束后帶有列別名。

Answer 3

注意，我將其寫為：

SELECT p.*,  
       (Total_Retail_Price * (1 - COALESCE(Discount, 0)) * Quantity) AS Rev 
FROM DATA.Cumulative_Profit_2013 AP

我發現很難Total_Retail_Price原始表達式中Total_Retail_Price的重復。

注意：所有答案均適用於SAS。