Database BA471 – Fall 2007 Dr. V.T. Raja Oregon State University

Databases – Part 1 : Outline Introduction Data Hierarchy Traditional file management Terminology Database DBMS Database Design Entity-Relationship Diagram

Data Hierarchy Bits Bytes (Kilo, mega, giga, tera, and peta bytes) Field (e.g., SSN, Student last name) Record File (e.g., Student file) Traditional File Management System Database

Traditional File Management Each application has specific data files related to it, containing all data needed by that application. Example: University File Management Environment Application used by Registrar’s Office Application used by Financial Aid Application used by COB Application used by Athletics Department

Some disadvantages associated with traditional file management Data Redundancy Data Inconsistency Lack of Data Integrity Duplication results in a need for more (time, space and cost) resources Application/Data Dependence Data Isolation Lack of Data Security

Terminology Database : An organized collection of data that serves many applications while minimizing the disadvantages associated with the traditional file management environment DBMS : Database Management System Software that: creates/maintains a database and enables storage and extraction of data/information for different business applications

Designing Databases Whatever DBMS you use, a database is only as good as its conceptual design. The conceptual design of a database is an abstract model of the database – based on the user/business perspective. It is common to use E-R diagrams for the conceptual (logical) design of a database.

Database Design: E-R Diagram Terminologies Entity Attributes Primary Key Relationships/Associations Entity Relationship Diagrams Logical view of database Database design documentation Facilitates communication between end-user and database developer

Entity-Relationship Diagrams: Notation Entity: Name of entity enclosed in a rectangular box; Attribute: Name of attribute enclosed within an oval shaped figure; a line connects attribute to its respective parent entity. No two attributes of an entity should have same name. Relationship: Name of relationship enclosed in a diamond shape, which is placed between two entities; 2 lines are drawn – each line connects the diamond to one of the entities. Primary Key: represented by underlining the attribute(s) that form the key.

Example Draw an ERD for the following information: SID, Sname, Address, Major, Phone, , Course#, CourseTitle, Instructor name, Instructor’s office, Instructor’s Address, Instructor’s phone#, course registration, grades and teaching assignments are to be stored. A student can take many courses A course could have different instructors in different terms An instructor can teach many courses

Different Types of Relationships Different types of relationships (between entities) are possible: m or m -1 m - n Recursive IS A relationship