Re: Debugging postmaster to fix possible bug in Postgres? Followup to "How do you select

On Thu, 13 Feb 2003 18:28:50 +0100, Nicholas Allen
<nallen(at)freenet(dot)co(dot)uk> wrote:
>Because the WHERE clause is directly affected by the ORDER BY clause.

No, it's not (at least in your query).

> If you
>leave out the order by clause then the row count will be completely different
>and therefore wrong.

I must be missing something. Please give an example.

> The ORDER BY clause is just as important as the WHERE
>clause when counting rows. It should be possible to get a count for the rows
>for any query that can be done which can return row data as I understand it.

If you have a set of numbers, say {1, 9, 5, 3, 7}, and want to know
how many elements of the set are <= 7 (SELECT COUNT(*) FROM s WHERE
n<=7), you simply look a each element - no matter in what order - and
increase your counter, if the element satifies your condition. I
can't see how you get different numbers when you count {1, 3, 5, 7},
{1, 5, 3, 7} or any other permutation.

>I have tried to find a definition for SQL SELECT command but everywhere I have
>looked so far makes no mention of this being invalid SQL syntax. Can you let
>me know where you got this information?

SQL92 says:
<direct select statement: multiple rows> ::=
<query expression> [ <order by clause> ]
[...]
3) Let T be the table specified by the <query expression>.

4) If ORDER BY is specified, then each <sort specification> in the
<order by clause> shall identify a column of T.

Servus
Manfred