Every language that I've ever used (other than APL) has the precedence of
"or" being less than "and". So I would always expect the "and" clauses to
be evaluated first, then the "or". Just like in math, where in an
equation, I expect that the multiplication (and) is done before the
addition (or). Unless modified by parentheses just as in your second
example.
On Sat, 12 Aug 2000, Philip Warner wrote:
>
> I have a peculiar problem that I can't reproduce on a trivial database:
>
> select product, priority, count(*) as completed from issue
> where
> product = 'DIS'
> and create_date < '1-Aug-2000' and finish_date >= '1-Aug-2000' or
> finish_date is null
> group by product, priority;
>
> This produces a list of all products - not just 'DIS'. If I put the last
> two clauses in parnthesis, then it works as expected:
>
> select product, priority, count(*) as completed from issue
> where
> product = 'DIS'
> and create_date < '1-Aug-2000' and (finish_date >= '1-Aug-2000' or
> finish_date is null)
> group by product, priority;
>
> Which makes me think that the precedence of 'or' is not what I expected. Is
> this a feature? If so, the fact that I get precisely the opposite behaviour
> in simple test databases must be a bug, I think.
>
> Any help or explanation would be appreciated...
>
>
>
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