SQL NOT IN 子句

我有一个查询未按预期工作

Q1:
SELECT id, name 
FROM vw_x 
WHERE id NOT IN (select pid from table_x)
GROUP BY id, name
Having max(c_date) > GETDATE()

Q2:
SELECT id, name 
FROM vw_x 
GROUP BY id, name
Having max(c_date) > GETDATE()

即使我知道这些 id 不在 table_x 中，Q1 也没有返回任何内容 Q2 正确运行，没有 NOT IN

我的查询可能有什么问题？

表中有一个 NULL 值

try this

SELECT id, name 
FROM vw_x 
WHERE id NOT IN (select pid from table_x where pid is not null)
GROUP BY id, name
Having max(c_date) > GETDATE()

or this

SELECT id, name 
FROM vw_x 
WHERE  NOT EXISTS (select 1 from table_x  where pid = vw_x.id  )
GROUP BY id, name
Having max(c_date) > GETDATE()

也可以看看选择一个表中不存在于另一表中的所有行 http://blogs.lessthandot.com/index.php/DataMgmt/DataDesign/the-ten-most-asked-sql-server-questions--1#4