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Home -> Community -> Mailing Lists -> Oracle-L -> RE: logical differing from physical
The table PERSON and the table CAR have a many-to-many relationship. To
represent this, you would create a join table (or associative table) that
contains an identifying foreign key relationship from PERSON and CAR (so the
primary key for the new child table would be a concatenated primary key
consisting of the foreign key from PERSON and the foreign key from CAR).
This way you can properly show that a person can own many cars and a car can
belong to many people without having to create excessive duplication of rows
in PERSON or CAR (if you put the foreign key for CAR directly into PERSON,
you will have to create a duplicate row for each person for each car they
have). HTH!
Jeffery Stevenson
Chief Database Geek
Medical Present Value, Inc.
Austin, TX
-----Original Message-----
From: root_at_fatcity.com [mailto:root_at_fatcity.com]On Behalf Of Weaver,
Walt
Sent: Wednesday, August 23, 2000 1:29 PM
To: Multiple recipients of list ORACLE-L
Subject: RE: logical differing from physical
Guess I'll have to show a bit of ignorance here. Why would this take 3 tables to implement properly?
--Walt Weaver
Bozeman, Montana USA
-----Original Message-----
Sent: Wednesday, August 23, 2000 10:48 AM
To: Multiple recipients of list ORACLE-L
4. Many to Many relationships. This only requires 2 tables to model, but at least 3 to implement. ( properly )
Many more I'm sure, but this illustrates the point.
Jared
--
Author: Weaver, Walt
INET: wweaver_at_rightnowtech.com
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