# Database Design

Database Design is the process of designing the general structure of the database.

* **Logical Design** deals with designing a database schema. We have a business decision (what attributes to record in the database?) and a Computer Science decision (how should the attributes be distributed acmong the various schemas?)
* **Physical Design** deals with the physical layout of the database, such as file organization and internal storage structures
* **Application-Level Design** deals with views, stored procedures and interfaces

Some common approaches for database design are:

* **Normalization Theory**\
  We formulate a set of schemas that can store information without redundancy and allow for easy retrieval. We then identify which designs are bad, test for them and convert them into good designs by following a set of rules. This will be discussed in detail later on.
* **Entity-Relationship Model**  \
  Every object is modeled as an entity and the relationship denotes the association among the different entities. Every entity has its own attributes. The following figure illustrates a simple ER Model:\
  ![](/files/-M5-0_GiPrTdI38C42pi)Here, instructor and department are entities with their attributes mentioned below them, and member is the relationship that associates an instructor with a department.


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