[thelist] Problem with distinct
Stephen Rider
evolt_org at striderweb.com
Fri Sep 7 16:26:36 CDT 2007
On Sep 7, 2007, at 4:04 PM, Bill Moseley wrote:
> Client says: "I want to be able to sort the widget list by its
> color".
>
> Developer: "But you can't do that because a widget might have more
> than one color. Which color would would you sort by?"
>
> Client: "90% of our widgets only have one color, so sort by that
> color. For
> the very few that have more than one color I don't care which one
> is used
> for sorting."
>
> test=> select distinct on (id) * from product_view;
> id | widget_name | color | size
> ----+-------------+-------+-------
> 1 | widget A | red | large
> 2 | widget B | red | large
> (2 rows)
>
> Cool! But wait:
>
> test=> select distinct on (id) * from product_view order by color;
> ERROR: SELECT DISTINCT ON expressions must match initial ORDER
> BY expressions
>
> Darn, that's not very helpful. What else to do?
Hi --
Maybe add another layer? Make a query without the sort, then a
second query pulls the first query and sorts it.
Stephen
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