Question

我有这个SQL表：

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

这个查询：

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

我想用 1 替换 NULL ，我想在PRICE列中进行乘法运算。我不想使用 UPDATE ，因为我无法更改table1中的值。

Answer 1

COALESCE返回其参数的第一个非空值

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

Answer 2

您可以使用coalesce表达式来获取值而不是null：

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

Answer 3

你也可以使用IFNULL：

SELECT id, description, quantity, each,
IFNULL(quantity,1)*each AS price
FROM Table

带有NULL行的MySql乘法列

3 个答案: