From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
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To: | Peter Schaefer <schaefer(at)cys(dot)de> |
Cc: | "pgsql-bugs(at)postgreSQL(dot)org" <pgsql-bugs(at)postgreSQL(dot)org> |
Subject: | Re: [BUGS] CREATE VIEW interp AS select DISTINCT itemkey from songs; |
Date: | 1999-10-13 14:27:22 |
Message-ID: | 20471.939824842@sss.pgh.pa.us |
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Lists: | pgsql-bugs |
Peter Schaefer <schaefer(at)cys(dot)de> writes:
> codiak=> CREATE VIEW interp AS select DISTINCT ON id id from interp;
What version are you using? The current development sources don't like
the above at all:
regression=> CREATE VIEW interp AS select DISTINCT ON id id from interp;
ERROR: Relation 'interp' does not exist
regression=> create table interp (id int);
CREATE
regression=> CREATE VIEW interp AS select DISTINCT ON id id from interp;
ERROR: Relation 'interp' already exists
regression=> CREATE VIEW interp1 AS select DISTINCT ON id id from interp;
ERROR: DISTINCT not supported in views
The reason for the last point is that DISTINCT requires sorting, and
the current implementation method for views doesn't allow a view to
specify an ordering. (CREATE VIEW ... SELECT ... ORDER BY doesn't
work either.)
You can work around this to some extent by using GROUP BY:
regression=> CREATE VIEW interp1 AS select id from interp group by id;
CREATE
although I think there may be some restrictions on grouped views too.
regards, tom lane
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