| From: | Raymond O'Donnell <rod(at)iol(dot)ie> |
|---|---|
| To: | Bill Thoen <bthoen(at)gisnet(dot)com> |
| Cc: | pgsql-general(at)postgresql(dot)org |
| Subject: | Re: Question About UNION |
| Date: | 2008-10-09 16:44:26 |
| Message-ID: | 48EE34EA.5090608@iol.ie |
| Views: | Raw Message | Whole Thread | Download mbox | Resend email |
| Thread: | |
| Lists: | pgsql-general |
On 09/10/2008 17:36, Bill Thoen wrote:
> I'm trying to combine two tables, but I only want unique records based
> on the first two columns. Can UNION be used to join three-column tables
> but only include records based on the uniqueness of the first two
> columns? If not, how would I do this with PostgreSQL 8.1?
How do you decide which records you want? - e.g. given the following rows...
(a, b, c)
(a, b, d)
...how do you decide whether you the one with c or the one with d?
Ray.
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Raymond O'Donnell, Director of Music, Galway Cathedral, Ireland
rod(at)iol(dot)ie
Galway Cathedral Recitals: http://www.galwaycathedral.org/recitals
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