Friday, February 21, 2014

Many to many relations in relational database design

Many to many relations are important in relational database design.
For example in publication database, one publication has many authors and one author has  many publications.
In publication table: pub_id is primary key
pub_id, pub_title, jour_name, pub_date, volume, start_page, end_page, pub_date

In author table: author_id is primary key
author_id, prefix,  firstnme, lastname, institute, position

 Bad design 1) in publication table, add author1, author2, author3 columns.
Bad design 2)  in publication table, add  one author  column, which requires 3,4,5 (authors are separated by comma) in input.

The good design is to  create another junction or linking table, i.e.
pub_id, author_id
(both of them are not primary keys)/


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