From: Tom Lane <tgl@sss.pgh.pa.us>
To: BigSmoke <bigsmoke@gmail.com>
Cc: pgsql-sql@postgresql.org
Subject: Re: unique constraint instead of primary key? what disadvantage(ODBC usage)?
Date: Thu, 09 Feb 2006 12:12:35 -0500
Message-ID: <2303.1139505155@sss.pgh.pa.us> (raw)
In-Reply-To: <1139502179.764894.35960@o13g2000cwo.googlegroups.com>
References: <20060208210455.5d6f5bf9.gry@ll.mit.edu>
<1139502179.764894.35960@o13g2000cwo.googlegroups.com>
"BigSmoke" <bigsmoke@gmail.com> writes:
> As far as I know, though, PRIMARY KEY does the same thing as UNIQUE NOT
> NULL in PostgreSQL.
They are 99.9% the same --- the *only* difference AFAIR is that PRIMARY
KEY establishes a default column-to-reference for FOREIGN KEY references
to the table. UNIQUE doesn't; you can make a FOREIGN KEY reference to a
column that's only UNIQUE, but you'll always have to specify which column.
regards, tom lane
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To: pgsql-sql@postgresql.org
Cc: tgl@sss.pgh.pa.us, bigsmoke@gmail.com
Subject: Re: unique constraint instead of primary key? what disadvantage(ODBC usage)?
In-Reply-To: <2303.1139505155@sss.pgh.pa.us>
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