MySQL的SUM和GROUP BY從AS柱

Question

table1的結構和樣本數據

+----+-------------+----------+------+-------+ 
| ID | DESCRIPTION | QUANTITY | EACH | PRICE | 
+----+-------------+----------+------+-------+ 
| 1 | Product 1 |  1 | 12 | 1*12 | 
| 2 | Product 2 |  2 | 3 | 2* 3 | 
| 3 | Prodcut 3 | NULL | 3 |  | 
| 4 | Product 1 |  2 | 10 | 2*10 | 
| 5 | Product 3 | NULL | 7 |  | 
+----+-------------+----------+------+-------+ 

MySQL查詢：

SELECT 
    DESCRIPTION, 
    QUANTITY, 
    EACH, 
    COALESCE(QUANTITY, 1) * EACH AS PRICE 
FROM table1 
GROUP BY DESCRIPTION 

我如何才能讓SUM爲PRICE柱和GROUP BY描述列？我不想使用UPDATE，因爲我無法更改table1中的值。

Answer 1

那麼爲什麼你不能在你的選擇列表中添加SUM(COALESCE(QUANTITY, 1) * EACH) AS PRICETOTAL。

Answer 2

SELECT 
    DESCRIPTION, 
    SUM(COALESCE(QUANTITY,1)*each) as 'Price' 
FROM table1 
GROUP BY DESCRIPTION 


returns 
DESCRIPTION Price 
Product 1 32 
Product 2 6 
Product 3 10