Re: Select distinct and order by.

On Wed, 11 Jul 2001, Carlos wrote:

> Select distinct field1, field2 from table1 order by field3;
>
> The value return by PQresultErrorMessage is:
>
> For SELECT DISTINCT, ORDER BY expressions must appear in target list

That's because this query is ambiguous.

What if table1 looks like this:

field1 field2 field3
------ ------ ------
a b 1
a b 3
c d 2

What should your query return then? Both

a b
c d

and

c d
a b

are valid, depending on which 'a b' row was chosen.

If 6.5.3 allowed that, it was a mistake to rely on it because the answer
is undefined.
--
Tod McQuillin