Re: [SQL] SELECT DISTINCT ON ... ORDER BY ...

I have the same on 6.4.2
Looks like a bug
Sincerely, Sergei

On Thu, 28 Jan 1999, Thomas Metz wrote:

> I have the following problem:
>
> Assuming the table TEST as follows:
>
> ID NAME
> -----------------
> 1 Alex
> 2 Oliver
> 1 Thomas
> 2 Fenella
>
>
> SELECT DISTINCT ON id id, name FROM test;
> produces:
>
> ID NAME
> -----------------
> 1 Alex
> 2 Oliver
>
>
> SELECT DISTINCT ON id, name FROM test ORDER BY name;
> produces:
>
> ID NAME
> -----------------
> 1 Alex
> 2 Fenella
> 1 Thomas
>
> I would have expected only two rows in both queries. I don't care which
> names actually appear in the output as long as they are sorted, but
> there should no longer be duplicate id's.
>
> If the table is as follows:
>
> ID NAME
> -----------------
> 2 Oliver
> 2 Alex
> 1 Thomas
> 1 Fenella
>
>
> SELECT DISTINCT ON id id, name FROM test;
> produces:
>
> ID NAME
> -----------------
> 1 Thomas
> 2 Oliver
>
>
> SELECT DISTINCT ON id, name FROM test ORDER BY name;
> produces:
>
> ID NAME
> -----------------
> 2 Alex
> 1 Fenella
> 2 Oliver
> 1 Thomas
>
> What seems to happen is that from the sorted table, duplicate id's are
> eliminated only if they are grouped. If there is no explicit sorting I
> assume the DISTINCT performs an implicit sorting on id and then
> eliminates records correctly. Is that the correct behaviour? Is there
> another (simple) way of getting the results I want?
>
> I am still using version 6.3
>
> tm
> --
> Thomas Metz
> GSF - National Research Center for Environment and Health
> Institute of Mammalian Genetics
>
>