Re: SELECT DISTINCT ON and ORDER BY

Yes, it works fine. Never came to my mind to simply use aggregate functions
on fields which I do not want in the group clause.

Is it common practice to do so in such cases? It seems odd somehow.

_____

Von: josep porres [mailto:jmporres(at)gmail(dot)com]
Gesendet: Freitag, 28. März 2008 14:15
An: Stanislav Raskin
Cc: pgsql-general(at)postgresql(dot)org
Betreff: Re: [GENERAL] SELECT DISTINCT ON and ORDER BY

maybe this?

select value, max(id) as id, max(order_field) as order_field
from mytable
group by value
order by 3

2008/3/28, Stanislav Raskin <sr(at)brainswell(dot)de>:

Hello everybody,

I have a table like this one:

id value order_field

1 10 3

2 12 4

3 10 1

4 5 8

5 12 2

What I want to do, is to do something like

SLECT DISTINCT ON (my_table.value)

my_table.id, my_table.value, my_table.order_field

FROM my_table

ORDER BY order_field

Hence selecting rows with distinct values, but primarily ordered by
order_field, instead of value, which is requires by DISTINCT ON.

The result in this case should be:

id value order_field

3 10 1

5 12 2

4 5 8

How do I do this? I do need order_field in the select list to use it in the
ORDER statement, which is why – as far as I can see – GROUP BY and SELECT
DISTINCT are useless. Did I miss out on something?

Thank you in advance