IMS 6217: Database Design & Entities 1 Dr. Lawrence West, MIS Dept., University of Central Florida Database Design--Topics DB Design Steps Information Elements Entities –Identifying –Defining Identifier Attributes

IMS 6217: Database Design & Entities 2 Dr. Lawrence West, MIS Dept., University of Central Florida Database Design Steps Identify “Information Elements” Identify Entities Identify Primary Keys Identify Relationships Fix Relationship Problems Identify Non-Key Attributes Fix Attribute Problems Address Performance Issues Build Application Objects (stored procedures, views) Design Reports List is not strictly sequential Some steps performed recursively Some steps require returning to previous steps

IMS 6217: Database Design & Entities 3 Dr. Lawrence West, MIS Dept., University of Central Florida Information Elements IS Design involves interviews with clients –Clients don’t understand our terminology or DB concepts (or they wouldn’t need us!) –We probably don’t understand much of theirs –Examine forms, reports & filing cabinets Interviews & research will result in a collection of "Information Elements" (my term) –Lists of items of concern to the client –Items that crop up in interviews & research –Items you recognize from your experience

IMS 6217: Database Design & Entities 4 Dr. Lawrence West, MIS Dept., University of Central Florida Information Elements Exercise Identify Information Elements for ______________________________________________

IMS 6217: Database Design & Entities 5 Dr. Lawrence West, MIS Dept., University of Central Florida Entities "A person, place, object, thing, event, or concept about which the organization wishes to maintain data" Examples from the university's database might be STUDENT, CLASS, and PROFESSOR Each entity in the final data model will become a table in the physical database It is important to distinguish between entities and attributes of an entity –Distinction may change with perspective We will also create new entities as we refine our data model

IMS 6217: Database Design & Entities 6 Dr. Lawrence West, MIS Dept., University of Central Florida Entity Identification Exercise Identify the Entities In the Information Elements Collection ______________________________________________

IMS 6217: Database Design & Entities 7 Dr. Lawrence West, MIS Dept., University of Central Florida Defining Entities It is amazingly important to explicitly define what is meant by each entity What is contained in the following entities? –Customer− Order –Sale− Employee Entity descriptions become part of the DB documentation (description property in SQL Server) You cannot assume that developers using the DB will have the save vision for the meaning of an entity that you do

IMS 6217: Database Design & Entities 8 Dr. Lawrence West, MIS Dept., University of Central Florida Entity Definition Exercise Define Sample Entities From the List of Entities [One occurrence of this entity represents…] _____________ See lesson on course lessons page on describing entities and attributes

IMS 6217: Database Design & Entities 9 Dr. Lawrence West, MIS Dept., University of Central Florida Identifier Attributes (Primary Keys) Identifier Attribute: An attribute whose value uniquely identifies each occurrence of an entity –SSN for student or faculty –VIN for an automobile –SKU for a retail product Composite Identifiers: More than one attribute is needed to uniquely identify an entity occurrence –Dept Code & Number for a course –Building Code & Room Number for a classroom Review Alternate Keys

IMS 6217: Database Design & Entities 10 Dr. Lawrence West, MIS Dept., University of Central Florida Identifier Attribute (Primary Key) Exercise Identify Primary Key Attributes For Selected Entities Identifier attribute/PK consistent with entity name and description? Is there a natural PK? Is an artificial PK needed (especially autonumber)? Are there alternate identifier attribute sets?