Jaime Casanova wrote:
> On Wed, Apr 7, 2010 at 10:30 PM, Warren Bell <warrenbe...@gmail.com> wrote:
> > Is there a way to create a unique constraint based on the content of a
> > field? For instance, say you have an integer field where you only want one
> > record with the number 1 in that field but there can be many records with
> > say the number 2 or any other single number in that field.
> >
>
> create unique index unique_field_idx
> on table1(field)
> where field = 1;
Wow, great idea. I never thought of partial indexes as a method for
unique qualification. I am glad to see our documentation mentions this
usage:
http://www.postgresql.org/docs/8.4/static/sql-createindex.html
Another possible application is to use WHERE with UNIQUE to enforce
uniqueness over a subset of a table.
--
Bruce Momjian <br...@momjian.us> http://momjian.us
EnterpriseDB http://enterprisedb.com
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