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Database Design 1: Introduction and Terminology CS 320
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Steps in Web/Database Development Project definition Identify site goals Analysis Specify what the site needs to do Design Specify how the site going to do what it needs to do in order to accomplish its goals Development Create the database Create the Web pages Test and deploy
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Design Steps Design the database Design the Web pages Static pages Dynamic Web pages that interact with the databases
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What is a Data Model? Precise description of the data content in a system Levels of data models: 1. Conceptual: describes WHAT data the system contains 2. Logical: describes HOW the database will be structured, regardless of the DBMS 3. Physical: describes HOW the system will be implemented using a specific DBMS
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Why create data models? To aid in the development of a sound database design Goal: to create database tables that do not contain duplicate data values that can become inconsistent
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Entity-Relationship Data Models Specify data items and relationships Classic, simplest Best for deriving a sound table design Many extensions/variations exist Basis for most other modeling approaches
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Sample Database (used in examples) CANDY_CUSTOMER CANDY_PURCHASE CANDY_CUST_TYPE CANDY_PRODUCT
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Creating an Entity-Relationship Model 1. Identify entities 2. Identify entity attributes and primary keys 3. Specify relationships
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Data Entities Entity A "thing" about which you want to store data in an application Key: Multiple instances of the entity must exist Goal: Store data about each entity in a separate table Example entities in CANDY database: CUSTOMER, PRODUCT, PURCHASE
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Database Vocabulary CANDY_PRODUCT Field: individual data item Record: collection of related fields Table: collection of related records
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ER Model Attributes Attribute A characteristic (field) of an entity that you want to store in the database Examples: CUST_ID, PROD_DESC Attribute value The value of a particular attribute for a particular instance of an entity Examples: 1, "Nuts Not Nachos"
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ER Model Relationships Specify how instances of one entity are related with instances of another entity
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Example Relationships
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Test Yourself: In a database for an Italian restaurant, ENTREE would be an example of a(n): a. Entity b. Attribute c. Entity instance d. Relationship
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Test Yourself: In a database for an Italian restaurant, ENTREE would be an example of a(n): a. Entity b. Attribute c. Entity instance d. Relationship
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Test Yourself: In a database for an Italian restaurant, ENTREE_PRICE would be an example of a(n): a. Entity b. Attribute c. Entity instance d. Relationship
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Test Yourself: In a database for an Italian restaurant, ENTREE_PRICE would be an example of a(n): a. Entity b. Attribute c. Entity instance d. Relationship
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