I have inherited maintenance of an in-house application along with a couple of views in our ERP system's database.
I have begun to suspect that my predecessor was drunk as a skunk when writing these views, or was making the queries deliberately complicated as a form job protection (if so, the joke is on me, because the guy quit).
One of the things that I find highly confusing about the views is that the WHERE-clause contains a sub-clause that looks a little bit like this:
SELECT ...
WHERE ...
OR ( (('*') IS NULL)
AND Project.Invalid = 0
AND ... )
OR ...
From my understanding, that ('*') IS NULL
part should basically be a no-op. Yet, when I comment that line out, the number of rows returned by the query jumps from 460 to ~350,000.
I am fairly confused by this, I would have expected no change at all in the number of results.
In the same query, another branch of the WHERE
-clause contained a similar sub-clause, ((-255) IS NULL)
, and when I commented that one out, the number of results stayed the same.
What is going on here? Is there something funky going on, or am I missing something obvious?
Thank you very, very much for any input!!!
Best Answer
('*') IS NULL
evaluates to false. As a result theOR
part also evaluates to false. We can use the simple rule:Of course as a result, if you comment out
(('*') IS NULL)
the result changes.Try commenting out the whole
OR
part:This should have no effect, due to the other rule: