Odd SQL behavior, I'm wondering why this works the way it does.
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by Matthew Vines
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Published on 2010-03-25T20:32:11Z
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2010/03/25
20:43 UTC
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Consider the following Transact sql.
DECLARE @table TABLE(val VARCHAR(255) NULL)
INSERT INTO @table (val) VALUES('a')
INSERT INTO @table (val) VALUES('b')
INSERT INTO @table (val) VALUES('c')
INSERT INTO @table (val) VALUES('d')
INSERT INTO @table (val) VALUES(NULL)
select val
from @table
where val not in ('a')
I would expect this to return
b, c, d, NULL
but instead it returns
b, c, d
Why is this the case? Is NULL not evaluated? Is NULL somehow in the set 'a'?
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