Database Essay

955 WordsJul 10, 20144 Pages
Chapter 3: Entity Relationship Model Database Design Process •Use a high-level conceptual data model (ER Model). • Identify objects of interest (entities) and relationships between these objects •Identify constraints (conditions) •End result is an E-R Diagram that captures all entity, relationship types and constraints Figure 3.1 Phases of Database Design Miniworld © Addison Wesley Longman, Inc. 2000, Elmasri/Navathe, Fundamentals of Database Systems, Third Edition Figure 3.1 A simplified diagram to illustrate the main phases of database design. REQUIREMENTS COLLECTION AND ANALYSIS Functional Requirements Database Requirements FUNCTIONAL ANALYSIS CONCEPTUAL DESIGN High-level Transaction Specification Conceptual Schema (In a high-level data model) DBMS-independent DBMS-specific LOGICAL DESIGN (DATA MODEL MAPPING) Logical (Conceptual) Schema (In the data model of a specific DBMS) APPLICATION PROGRAM DESIGN PHYSICAL DESIGN TRANSACTION IMPLEMENTATION Internal Schema Application Programs Example Database Application (Company Database) Company organized into DEPARTMENTs. Each department has unique name and a particular employee who manages the department. Start date for the manager is recorded. Department may have several locations. A department controls a number of PROJECTs. Projects have a unique name, number and a single location. Company’s EMPLOYEEs name, ssno, address, salary, sex and birth date are recorded. An employee is assigned to one department, but may work for several projects (not necessarily controlled by her dept). Number of hours/week an employee works on each project is recorded; The immediate supervisor for the employee. Employee’s DEPENDENTs are tracked for health insurance purposes (dependent name, birthdate, relationship to employee). Figure 3.2: ER Diagram Figure 3.2 Fname Minit ER

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