In the preceding course Relational Database Design
, you created a Entity Relationship diagram to track
- the products offered by and
- orders placed with Stories on CD, Inc.,
a fictional company that sells books on CD principally by mail order.
In this module you will use a modified version of that ER diagram to derive the database objects used to represent CDs, distributors, and orders in the database.
When you begin to design the structure of your database, you will represent entities in the database as relations
Once you have created relational notations based on the entities in your ER diagram, you can analyze them with an eye toward:
Ensuring that information is delivered in a consistent manner
Eliminating data redundancy
Preserving existing data when deleting unwanted data
It is possible to perform the analysis in this module and the next with the entities written as they are in the ER diagram, but
representing the entities in relational notation makes the task easier in three important ways:
Representing an entity in a text format is much more compact than representing the same entity graphically.
Some of the concepts in this course, such as functional dependencies and transitive dependencies,
are customarily written (and are easier to explain) using relational notation.
Finally, if you choose to continue studying database design, you will almost certainly encounter relational
notation in other courses or books.
Relational Database Notation
Being able to read and write relational notation is a valuable skill.
The next lesson outlines the characteristics of tables
, which are the objects that store database data.