选择不为null

Question

在SQL查询中，我想选择一个可空列作为布尔值，具体取决于它是否为null。简单的例子：

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”用于true，“0”用于false。