Select 不为空

Question

在 SQL 查询中，我想 select 一个可为空的列作为布尔值，具体取决于它是否为空。简单示例：

SELECT name AS UserName, age AS UserAge, (birthday IS NOT NULL) AS HasEnteredBirthday
FROM users

结果：

Incorrect syntax near the keyword 'IS'.

预期结果：

Peter 31 1
Greg  54 0

Answer 1

并非所有数据库都支持布尔类型。您可以将 case 用作：

SELECT name AS UserName, age AS UserAge,
       (CASE WHEN birthday IS NOT NULL THEN 'true' ELSE 'false' END) AS HasEnteredBirthday
FROM users;

通常，整数“1”代表真，“0”代表假。

Select not null as