sql server not in 查询没结果

sql server not in 查询没结果Posted on 今天使用SQL Server 时，遇到使用not in 和not exist的查询结果有差异：not in 查询没结果。 原因：not in 遇到null就不工作了。 摘录： SELECT foreignStockId Probably returns aNULL. Try IdStock Descr stock a N

sql server not in 查询没结果 Posted on

今天使用SQL Server 时，网站空间，遇到使用not in 和not exist的查询结果有差异：not in 查询没结果。

原因：not in 遇到null就不工作了。

摘录：

SELECT foreignStockId

Probably returns a NULL. Try

IdStock Descr stock

a NOT IN (x,y,NULL) Will always return no results as it is equivalent to

ax and ay and aNULL which is

true and true and unknown

Which evaluates to unknown under the rules of three valued logic.

I normally use NOT EXISTS for this type of query

stock.descr stock p

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