To divide the information into tables, Choose the major entities, or subjects:
For example, after finding and organizing information for a product sales database, suppose the major entities are the products, the suppliers, the customers, and the orders. Therefore, it makes sense to start out with these four tables: one for facts about products, one for facts about suppliers, one for facts about customers, and one for facts about orders.
When you design your database, always try to record each fact just once. If you find yourself repeating the same information in more than one place, such as the address for a particular supplier, place that information in a separate table. Once you have chosen the subject that is represented by a table, columns in that table should store facts only about the subject. For instance, the product table should store facts only about products.
For example, after finding and organizing information for a product sales database, suppose the major entities are the products, the suppliers, the customers, and the orders. Therefore, it makes sense to start out with these four tables: one for facts about products, one for facts about suppliers, one for facts about customers, and one for facts about orders.
When you design your database, always try to record each fact just once. If you find yourself repeating the same information in more than one place, such as the address for a particular supplier, place that information in a separate table. Once you have chosen the subject that is represented by a table, columns in that table should store facts only about the subject. For instance, the product table should store facts only about products.
