ch040 - Concepts of Database Management Sixth Edition...

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Concepts of Database Management Sixth Edition Chapter 4 The Relational Model 3: Advanced Topics
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Concepts of Database Management 2 Objectives Define, describe, and use views Use indexes to improve database performance Examine the security features of a DBMS Discuss entity, referential, and legal-values integrity
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Concepts of Database Management 3 Objectives (continued) Make changes to the structure of a relational database Define and use the system catalog Discuss stored procedures and triggers
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Concepts of Database Management 4 Views View: application program’s or individual user’s picture of the database Less involved than full database Simplification Security
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Concepts of Database Management 5 Views (continued) Defining query: SELECT command that creates a view Indicates what to include in the view Query acts as a window into the database Does not produce a new table Query that involves a view DBMS does not execute the query in this form Query actually executed is created by merging this query with the query that defines the view
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Concepts of Database Management 6 Views (continued) CREATE VIEW Housewares AS SELECT PartNum, Description, OnHand, Price FROM Part WHERE Class='HW' ; FIGURE 4-1: Housewares view
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Concepts of Database Management 7 Views (continued) FIGURE 4-2: Housewares view of the Premiere Products database
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Concepts of Database Management 8 Views (continued) To create a view in Access, create and save a query Changing field names in a view SQL: include the new field names in the CREATE VIEW command Access: precede the name of the field with the desired name, followed by a colon Row-and-column subset view Subset of rows and columns in an individual table
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Concepts of Database Management 9 Views (continued) FIGURE 4-3: Access query design of the Housewares view
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Concepts of Database Management 10 Views (continued) FIGURE 4-5: Access query design of the Housewares view with changed field names
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Concepts of Database Management 11 Views (continued) A view can join two or more tables Advantages of views Data independence Each user has his or her own view View should contain only fields required by the user Greatly simplifies user’s perception of database Security
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Concepts of Database Management 12 Indexes Conceptually similar to book index Increase data retrieval efficiency Record numbers automatically assigned and used by DBMS Index key: field or combination of fields on which index is built Advantages Makes some data retrieval more efficient
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Concepts of Database Management 13 Indexes (continued) FIGURE 4-10: Customer table with record numbers
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Concepts of Database Management 14 Indexes (continued) FIGURE 4-11: Index for the Customer table on the CustomerNum field
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ch040 - Concepts of Database Management Sixth Edition...

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