Re: help with a view (join-query)
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Тема | Re: help with a view (join-query) |
Дата | |
Msg-id | 02dd01c65083$2ec3f590$6402a8c0@iwing обсуждение исходный текст |
Ответ на | help with a view (join-query) (<me@alternize.com>) |
Список | pgsql-novice |
thanks alot - DISTINCT ON has exactly the behaviour i was looking for! - thomas ----- Original Message ----- From: "Bruno Wolff III" <bruno@wolff.to> To: <me@alternize.com> Cc: <pgsql-novice@postgresql.org> Sent: Sunday, March 26, 2006 1:59 AM Subject: Re: [NOVICE] help with a view (join-query) > On Fri, Mar 24, 2006 at 19:36:34 +0100, > me@alternize.com wrote: >> hi list >> >> currently in our database, a "person" contains a relation to one or more >> "events". i now need a view where each person is listed exactly once, and >> to each person only one (of possible more) events is listed. it does not >> matter which ones of the events are shown. when doing a normal JOIN, the >> resultset might return more than one record per person (for each event >> one line). >> is there an easy way to build a query that fullfills my needs? i'd rather >> not check programmatically if i already listed the person or not. > > You could use the Postgres specific extension DISTINCT ON to do this. You > can > even use ORDER BY to make which row you grab deterministic. > > ---------------------------(end of broadcast)--------------------------- > TIP 5: don't forget to increase your free space map settings >
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