tailieunhanh - Lecture Fundamentals of database systems: Chapter 3 - Emasri, Navathe

In chapter 3, we follow the traditional approach of concentrating on the database structures and constraints during conceptual database design. The design of application programs is typically covered in software engineering courses. this chapter also present the modeling concepts of the Entity-Relationship (ER) model, which is a popular high-level conceptual data model. | Overview of Database Design Process Example Database Application COMPANY ER Model Concepts Entities and Attributes Entity Types Value Sets and Key Attributes Relationships and Relationship Types Weak Entity Types Roles and Attributes in Relationship Types ER Diagrams - Notation ER Diagram for COMPANY Schema Alternative Notations - UML class diagrams others Two main activities Database design Applications design Focus in this chapter on database design To design the conceptual schema for a database application Applications design focuses on the programs and interfaces that access the database Generally considered part of software engineering Copyright 2007 Ramez Elmasr and Shamkant B. Navathei lide 3- 3 Copyright 2007 Ramez Elmasr and Shamkant B. Navathei lide 3-4 We need to create a database schema design based on the following simplified requirements of the COMPANY Database The company is organized into DEPARTMENTs. Each department has a name number and an employee who manages the department. We keep track of the start date of the department manager. A department may have several locations. Each department controls a number of projects. Each project has a unique name unique number and is located at a single location. Copyright 2007 Ramez Elmasr and Shamkant B. Navathei lide 3- 6 1 We store each EMPLOYEE S social security number address salary sex and birthdate. Each employee works for one department but may work on several projects. We keep track of the number of hours per week that an employee currently works on each project. We also keep track of the direct supervisor of each employee. Each employee may have a number of dependents. For each dependent we keep track of their name sex birthdate and relationship to the employee. Entities and Attributes Entities are specific objects or things in the mini-world that are represented in the database. For example the EMPLOYEE John Smith the Research Department the ProductX PROJECT Attributes are properties used to .