sqlserver not in 查询结果处理的问题

Question

我的目的是想查询没有父节点 也就是说是根节点

SELECT t1.Id FROM dbo.T_Code as t1 WHERE CodeTypeId='108' AND Name = '非业务'
and t1.Id in(select t2.ParentID from dbo.T_Code as t2 where CodeTypeId='108'AND Name = '非业务')

select t2.ParentID from dbo.T_Code as t2 where CodeTypeId='108'AND Name = '非业务'

查询结果：
NULL
00000000-0000-0000-0000-000000000959
00000000-0000-0000-0000-000000000960
SELECT t1.Id FROM dbo.T_Code as t1 WHERE CodeTypeId='108' AND Name = '非业务'
查询结果：
00000000-0000-0000-0000-000000000959
00000000-0000-0000-0000-000000000960
00000000-0000-0000-0000-000000000961
我的目的是查询出
00000000-0000-0000-0000-000000000961这条记录
但是这样结果却查询不出来

Answer 1

查找不出来是因为 NULL 引起的
SELECT t1.Id FROM dbo.T_Code as t1 WHERE CodeTypeId='108' AND Name = '非业务'
and t1.Id not in(select t2.ParentID from dbo.T_Code as t2 where CodeTypeId='108'AND Name = '非业务' AND t2.ParentID is not null)
修改为这样就可以了