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我已经使用联合查询合并了三个表,并为所有列创建了按功能分组。如何在SQL Server中将可空值更改为非空值?
这里是我的代码:
select
Id,
Firstname,
Mark1, Mark2, Mark3
from
(select
Id, Firstname, Null as Mark1, Null as Mark2, Null as Mark3
from
Parent
union
select
Id, Null as Firstname, Mark1, Mark2, Null as Mark3
from
Child
union
select
Id, Null as Firstname, Null as Mark1, Null as Mark2, Mark3
from
Mark) t
where
Mark3 is not null
group by
Id, Firstname, Mark1, Mark2, Mark3
在这里,我已经设置mark3
不是null使用WHERE条件,所以我的问题是如何改变空值不为空的使用WHERE条件的字段的休息吗?