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!!!
('*') IS NULL evaluates to false. As a result the
OR part also evaluates to false. We can use the simple rule:
(FALSE AND Something AND Something_Else AND ... ) = FALSE
Of course as a result, if you comment out
(('*') IS NULL) the result changes.
Try commenting out the whole
SELECT ... WHERE ... -- OR ( (('*') IS NULL) -- AND Project.Invalid = 0 -- AND ... ) OR ...
This should have no effect, due to the other rule:
(FALSE OR Something OR Something_Else OR ... ) = (Something OR Something_Else OR ... )