UMD CMSC 424 - Database Design (54 pages)

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Database Design



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Database Design

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Pages:
54
School:
University of Maryland, College Park
Course:
Cmsc 424 - Database Design
Database Design Documents

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CMSC424 Database Design Instructor Amol Deshpande amol cs umd edu CMSC424 Spring 2005 Data Modeling Goals Conceptual representation of the data Reality meets bits and bytes Must make sense and be usable by other people Today Entity relationship Model Relational Model CMSC424 Spring 2005 Motivation You ve just been hired by Bank of America as their DBA for their online banking web site You are asked to create a database that monitors customers accounts loans branches transactions Now what CMSC424 Spring 2005 Database Design Steps Entity relationship Model Typically used for conceptual database design Three Levels of Modeling info Conceptual DB design Conceptual Data Model Logical DB design Logical Data Model Relational Model Typically used for logical database design Physical DB design Physical Data Model CMSC424 Spring 2005 4 Entity Relationship Model Two key concepts Entities An object that exists and is distinguishable from other objects Examples Bob Smith BofA CMSC424 Have attributes people have names and addresses Form entity sets with other entities of the same type that share the same properties Set of all people set of all classes Entity sets may overlap Customers and Employees CMSC424 Spring 2005 Entity Relationship Model Two key concepts Relationships Relate 2 or more entities E g Bob Smith has account at College Park Branch Form relationship sets with other relationships of the same type that share the same properties Customers have accounts at Branches Can have attributes has account at may have an attribute start date Can involve more than 2 entities Employee works at Branch at Job CMSC424 Spring 2005 ER Diagram Starting Example access date cust name number cust id customer has account cust street cust city balance Rectangles entity sets Diamonds relationship sets Ellipses attributes CMSC424 Spring 2005 7 Rest of the class Details of the ER Model How to represent various types of constraints semantic information etc Design issues A detailed example



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