Jaime Casanova wrote: > On Wed, Apr 7, 2010 at 10:30 PM, Warren Bell <warrenbell2@xxxxxxxxx> 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 <bruce@xxxxxxxxxx> http://momjian.us EnterpriseDB http://enterprisedb.com -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
