用NULL MySQL的乘法列，0行

Question

我有這樣的MySQL表：

+----+-------------+----------+------+-------+ 
| ID | DESCRIPTION | QUANTITY | EACH | PRICE | 
+----+-------------+----------+------+-------+ 
| 1 | Product 1 |  1 | 12 | 1*12 | 
| 2 | Product 2 |  2 | 3 | 2* 3 | 
| 3 | Product 3 | NULL | 3 |  | 
| 4 | Product 4 |  0 | 7 |  | 
+----+-------------+----------+------+-------+ 

而這個查詢：

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

我想替換NULL和0與1，我想使乘以PRICE列。我不想使用UPDATE，因爲我無法更改table1中的值。 謝謝！

Answer 1

試試下面的查詢

SELECT 
    DESCRIPTION, 
    QUANTITY, 
    EACH, 
    COALESCE(IF(QUANTITY = NULL OR QUANTITY = 0,1,QUANTITY), 1) * EACH AS PRICE 
FROM table1 

Answer 2

這聽起來像你想CASE：

SELECT DESCRIPTION, QUANTITY, EACH, 
     ((CASE WHEN QUANTITY IS NULL THEN 0 
       WHEN QUANTITY = 0 THEN 1 
       ELSE QUANTITY 
     END) * EACH 
     ) AS PRICE 
FROM table1; 

Answer 3

SELECT 
    DESCRIPTION, 
    QUANTITY, 
    EACH, 
    IF(QUANTITY,QUANTITY, 1) * EACH AS PRICE 
FROM table1 

SQL Fiddle