如何在Tuple Criteria MYSQL中查询空值

Question

MYSQL查询:

select * from CLASS where (CLASS_ID, CLASS_NAME) = (1, "FIRST");

同样，我需要一个包含空值的元组，如

select * from CLASS where (CLASS_ID, CLASS_NAME) = (1, null);

但是上面的空值查询在mysql中不起作用

谁能帮我构造查询?

Answer 1

不能使用比较运算符检查NULL值。您唯一的选择是使用IS NULL。

你可以这样写:

(CLASS_ID, CLASS_NAME) = (1, "FIRST") OR (CLASS_ID = 1 AND CLASS_NAME IS NULL)