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composite primary key to foreign key

From: "Ryan Vaughan" <ryanv(at)mminternet(dot)com>
To: <pgsql-novice(at)postgresql(dot)org>
Subject: composite primary key to foreign key
Date: 2004-03-12 19:52:05
Message-ID: twig.1079121125.97560@mminternet.com (view raw or flat)
Thread:
Lists: pgsql-novice
I have a table with 4 columns, 3 of which make up a composite primary key. 
None of these columns are unique, but the combination of the the three 
primary keys will be unique:

CREATE TABLE Table1 (
   col1 integer,
   col2 varchar(20),
   col3 varchar(20),
   col4 varchar(20),
   CONSTRAINT PRIMARY KEY (col1, col3, col4)
);

In another table I have 3 columns:

CREATE TABLE Table2 (
   field1 integer,
   field2 integer,
   field3 integer,
);

I'd like to have field2 in table2 be a foreign key of col1 in table1.  Since 
col1 is not unique, is this possible or do I have to either bring in 
extraneous data from table1...col1, col2, and col3, or create some unique 
counter in table1 to use as reference?  All I care about in field2 of table2 
is that it matches something in col1 in table1, I don't want the other data 
in table1.  I've searched archives but maybe I'm not looking for the right 
thing.  Thanks.

-Ryan

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