On Oct 6, 2011, at 9:34, Rich Shepard <rshepard@appl-ecosys.com> wrote:
> On Wed, 5 Oct 2011, David Johnston wrote:
>
>> 2) "Window" - max(quant) OVER (PARTITION BY ...)
>
> Hmm-m-m. I have a problem here emulating the example on the document page.
> Regardless of which column is first after SELECT postgres tells me that
> column does not exist.
>
> select site_id, sample_date, param, max(quant) over (partition by param)
> chemistry;
> ERROR: column "site_id" does not exist
> LINE 1: select site_id, sample_date, param, max(quant) over (partiti...
Missing the FROM before chemistry
> ^
> select str_name, site_id, sample_date, param, max(quant) over (partition by
> str_name) chemistry;
> ERROR: column "str_name" does not exist
> LINE 1: select str_name, site_id, sample_date, param, max(quant) ove...
> ^
> What am I doing incorrectly here?
>
> Also, with the window function can I limit the output to a single str_name
> and param?
Not directly. After you create the windowed result you can turn it into a sub-query and filter that. The other form
suggested(where quant = select max(quant) from chemistry where ...) is probably a better performer though for your need
-I did't read the subject line closely enough and my two options don't directly give you what you are looking for.
Thoughera ing the window query and then adding a (where quant_max = quant) clause would get you closer; quant_max being
thecolumn alias for the window expression.
>
> Rich
>
David J.
