SQL查询中的Cast函数

Question

我正在尝试在CAST()和datetime功能上使用NULL功能。

我的查询是这样的：

where  [closed_at] = '' or  Cast ([closed_at]  as datetime) > = '09-01-2011 00:00' 

     and  [class_name] in ('Job' ,'Education');

Answer 1

您将使用IS NULL条件

where ([closed_at] is NULL or Cast ([closed_at] as datetime) > = '09-01-2011 00:00') and  [class_name] in ('Job' ,'Education');

或

where Cast (ISNULL([closed_at],'09-01-2011 00:00') as datetime) > = '09-01-2011 00:00') and  [class_name] in ('Job' ,'Education');