ER-Diagrams - The Database Design Process Prepared by John...

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The Database Design Process Prepared by John Macdonald Lectured by Kumari Gurusamy Oct 4 2016
Entities and Relationships Entity - an object within a database which represents some particular aspect of the business to which the database pertains. A business narrative will identify major objects, people or events which play a role in collecting and manipulating an organization s data; Each of these objects, people or events becomes an entity in your relational database.
Entities and Relationships Each entity is represented in the database as a table. Each table has one or more columns, which represent particular characteristics of each entity. Database designers call these characteristics attributes.
Entities and Relationships Relationships- the links which connect different entities together in a meaningful way. Establishing these relationships is the job of the business narrative; it is the job of the database designer to build these relationships into the database correctly. An Entity-Relationship diagram is a tool which helps the designer identify and construct these relationships.
The Entity-Relationship Diagram An Entity-Relationship (ER) diagram falls between the business narrative and the working database. The designer uses an ER diagram as a tool to establish a conceptual structure of the client s data needs. Once the designer creates the ER diagram, it can be reviewed and modified, and later used to develop the physical structure of the database.
The Entity-Relationship Diagram Benefits: Is easily understood; Can be easily developed and refined; Displays the scope of the organization's information requirements; and Provides a framework for integrating application packages and development projects.
The Entity-Relationship Diagram
Components of ER Diagrams Entities Objects that the client requires information about. Each entity is represented by a table in the database structure. Each entity must be a single, well-defined component of the system which the database represents
Entities Each entity is an abstraction of an object.

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