sql-server - 如何在日期时间字段中分配空值

Question

我努力了：

CAST(NULL AS DATETIME) AS Exit_T.

给我以下错误：

将 char 数据类型转换为 datetime 数据类型会导致 datetime 值超出范围。

我们可以为DateTime字段分配空值吗？在查询达到某些条件后我需要这个

Answer 1

What are you trying to do? You don't typically use NULL in a cast. You would assign the keyword NULL to the value of the field. Nulls are acceptable in DateTime fields if you allow it.

Answer 2

如果datetimefield 是NULL-able 字段，我们可以分配NULL值，否则，我们不能分配NULL值。

看看问题不在于演员阵容，而必须来自其他地方：

select CASE(NULL AS DATETIME) AS Exit_T;