在MySQL中，为什么我的NULL值不能正确比较？

Question

我有以下表

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 | 
+------+------+---+ 

预期的效果

+------+------+---+ 
| 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

使用这个代替：

IF Age IS NULL 

使用NULL实际上将表示空值，而“NULL”将充当字母N-U-L-L的字符串。根本不一样。

最终查询：

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