在MySQL中为什么我的NULL值不能正确比较？

Question

我有下表

Select * from Peeps
Id Name Age 
1  Sam  16
2  John NULL


Select 
Name, 
Age,
(If Age=NULL,1,0) AS Z
from peeps;

结果：

+------+------+---+
| name | age  | Z |
+------+------+---+
| Sam  |   16 | 0 |
| John | NULL | 0 |
+------+------+---+

期望的结果

+------+------+---+
| name | age  | Z |
+------+------+---+
| Sam  |   16 | 0 |
| John | NULL | 1 |
+------+------+---+

Answer 1

尝试：

Select 
Name, 
Age,
(If Age IS NULL,1,0) AS Z
from peeps;

http://dev.mysql.com/doc/refman/5.1/en/working-with-null.html

Answer 2

请改用：

IF Age IS NULL

使用NULL实际上表示空值，而“NULL”将作为字符串，其中包含字母N-U-L-L。完全不一样。

最终查询：

SELECT Name, 
       Age,
       (IF Age IS NULL, 1, 0) AS Z
  FROM peeps