Whats the master / detail relationship in database?

Databases that are efficiently designed include multiple tables. The goal of table design is to store all the information you need in an accessible, efficient manner. Therefore, you want to break down a database into tables that identify the separate entities (such as persons, places, and things) and activities (such as events, transactions, and other occurrences) important to your application. To better define your tables, you need to identify and understand how they relate to each other. Creating several small tables and linking them together reduces the amount of redundant data, which in turn reduces potential errors and makes updating information easier.

http://techpubs.borland.com/books/jbuilder/jbuilder2/jbuilder/database/prov_masterdetail.html

for more efficient database,

You need to determine the tables by categories, delimit the activities and determine the primary and foreign keys.

have more precision in the tables relate, depending on the degree of liability.

one to many relationshipexample:categories - > products relationship :)that's it !