CIS 210 Systems Analysis and Development Week 6 Part II Designing Databases,

Objectives Upon completion of part II you will be able to: –Understand and be able to explain the concepts related to key database design terminology –Understand and be able to transform E-R diagrams into an equivalent set of well-structured and normalized relationships –Understand and be able to merge normalized relations from several user views into a consolidated set of well-structured relations –Understand and be able to explain the concepts related to storage formats in database tables –Understand and be able to translate well-structured relations into efficient database tables –Understand and be able to explain the concepts related to different methods of storing data in computer files

Overview Database Design Guidelines –Database files –Logical design –Physical design Design Purposes –Table structure –Logical design –Physical design –Translate relational database model –Choose storage technologies

Database Design Logical Database Design –Four key steps Develop model Combine requirements Translate conceptual model Compare logical model with E-R model Physical Database Design –Use results of logical design –Attributes –Descriptions of data –Expectations –Descriptions of technologies Deliverables –Normalized relations –Specifications for computer files

Relational Database Model Overview –Data in the form of tables (relations) –Named columns –Unnamed rows Properties of Relations –Simple entries in cells –Column entries from the same set of values –Unique rows –Interchanged sequence of columns –Interchanged sequence of rows Well-Structured Relations –Minimum redundancy –Modification without inconsistency

Normalization Defining Normalization –Converting complete structures into simple stable data structures –Based on well-accepted principles and rules Functional Dependence and Primary Keys Second Normal Form (2NF) Third Normal Form (3NF) –Foreign key –Referential integrity

Transforming Diagrams Into Relations Represent Entities –Each entity type becomes a relation –Identifier becomes primary key –Other attributes become nonprimary keys Represent Relationship –Each relationship must be represented Normalize the Relations Merge the Relations

Physical File and Database Design Designing Fields –Choosing data types Minimize storage space Represent all possible values Improve data integrity Support data manipulations –Controlling data integrity Default value Range control Referential integrity Null value control

Physical File and Database Design Designing Physical Tables –Overview Physical table Denormalization –Arranging table rows Sequential file organization Indexed file organization Hashed file organization –Designing controls for files File restoration techniques

Summary Logical Database Design Normalization Transforming Diagrams Physical File and Database Design