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ch060 - Concepts of Database Management Sixth Edition...

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Concepts of Database Management Sixth Edition Chapter 6 Database Design 2: Design Method
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Concepts of Database Management 2 Objectives Discuss the general process and goals of database design Define user views and explain their function Define Database Design Language (DBDL) and use it to document database designs Create an entity-relationship (E-R) diagram to visually represent a database design Present a method for database design at the information level and view examples illustrating this method
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Concepts of Database Management 3 Objectives (continued) Explain the physical-level design process Discuss top-down and bottom-up approaches to database design and examine the advantages and disadvantages of both methods Use a survey form to obtain information from users prior to beginning the database design process Review existing documents to obtain information prior to beginning the database design
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Concepts of Database Management 4 Objectives (continued) Discuss special issues related to implementing one-to-one relationships and many-to-many relationships involving more than two entities Discuss entity subtypes and their relationships to nulls Learn how to avoid potential problems when merging third normal form relations Examine the entity-relationship model for representing and designing databases
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Concepts of Database Management 5 Introduction Two-step process for database design Information-level design : completed independently of any particular DBMS Physical-level design : information-level design adapted for the specific DBMS that will be used Must consider characteristics of the particular DBMS
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Concepts of Database Management 6 User Views User view : set of requirements necessary to support operations of a particular database user Cumulative design : supports all user views encountered during design process
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Concepts of Database Management 7 Information-Level Design Method For each user view: 1. Represent the user view as a collection of tables 2. Normalize these tables 3. Identify all keys in these tables 4. Merge the result of Steps 1 through 3 into the cumulative design
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Concepts of Database Management 8 Represent the User View As a Collection of Tables Step 1: Determine the entities involved and create a separate table for each type of entity Step 2: Determine the primary key for each table Step 3: Determine the properties for each entity Step 4: Determine relationships between the entities One-to-many Many-to-many One-to-one
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Concepts of Database Management 9 Represent the User View As a Collection of Tables (continued) One-to-many relationship: include primary key of the “one” table as a foreign key in the “many” table Many-to-many relationship : create a new table whose primary key is the combination of the primary keys of the original tables One-to-one relationship : simplest implementation is to treat it as a one-to-many relationship
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