McGraw-Hill/Irwin Copyright © 2007 by The McGraw-Hill Companies, Inc. All rights reserved. Chapter 10 Application Development with Views

10-2 Outline  Background  Creating views and using views  Processing queries that reference views  Updatable views  Data requirements for hierarchical forms  Data requirements for reports

10-3 What is a View?  Derived table  Behaves like a base table (virtual) with some restrictions for view usage in modification statements  Stored query

10-4 View Advantages  Reduce impact of database definition changes  Simplify database usage  Unit of database security  Can be a performance penalty on complex views

10-5 Three Schema Architecture

10-6 View Definition Example Example 1: Create a view consisting of offerings taught by faculty in the MS department. CREATE VIEW MS_View AS SELECT OfferNo, Course.CourseNo, CrsUnits, OffTerm, OffYear, Offering.FacSSN, FacFirstName, FacLastName, OffTime, OffDays FROM Faculty, Course, Offering WHERE FacDept = 'MS' AND Faculty.FacSSN = Offering.FacSSN AND Offering.CourseNo = Course.CourseNo

10-7 Column Renaming Example 2: create a view containing offering data and the number of enrolled students. CREATE VIEW Enrollment_View ( OfferNo, CourseNo, Term, Year, Instructor, NumStudents ) AS SELECT Offering.OfferNo, CourseNo, OffTerm, OffYear, FacLastName, COUNT(*) FROM Offering, Faculty, Enrollment WHERE Offering.FacSSN = Faculty.FacSSN AND Offering.OfferNo = Enrollment.OfferNo GROUP BY Offering.OfferNo, CourseNo, OffTerm, OffYear, FacFirstName, FacLastName

10-8 Using Views Example 3 SELECT OfferNo, CourseNo, FacFirstName, FacLastName, OffTime, OffDays FROM MS_View WHERE OffTerm = 'SPRING' AND OffYear = 2003 Example 4 SELECT OfferNo, Instructor, NumStudents, CrsUnits FROM Enrollment_View, Course WHERE Enrollment_View.CourseNo = Course.CourseNo AND NumStudents < 5

10-9 Processing View Queries  Materialization  Execute two queries  Large overhead  Preferred in static environments such as data warehouses (Chapter 16)  Modification  Substitute view definition for view references  Execute one query  Incurs little overhead  Not possible for all view queries

10-10 View Modification

10-11 View Materialization

10-12 Modification Examples Example 5: Query using a view SELECT OfferNo, CourseNo, FacLastName FROM MS_View WHERE OffYear = 2006 Example 6: Modified query SELECT OfferNo, Course.CourseNo, FacLastName FROM Faculty, Course, Offering WHERE FacDept = 'MS' AND OffYear = 2006 AND Faculty.FacSSN = Offering.FacSSN AND Offering.CourseNo = Course.CourseNo

10-13 Single Table Updatable Views  Support modification statements  Rules for single table updatable views  1-1 correspondence between view rows and base table rows  View includes PK of base table  View includes all required columns  View definition does not have GROUP BY or DISTINCT

10-14 Updatable View Examples Example 7: Single table updatable view CREATE VIEW Fac_View1 AS SELECT FacSSN, FacFirstName, FacLastName, FacRank, FacSalary, FacDept, FacCity, FacState, FacZipCode FROM Faculty WHERE FacDept = 'MS' Example 8: View update UPDATE Fac_View1 SET FacSalary = FacSalary * 1.1 WHERE FacRank = 'ASST'

10-15 View Update with Side Effects Modify column used in the WHERE condition of a view definition Use WITH CHECK OPTION clause to prevent Example 9: Change the department of rows in the Fac_View1 UPDATE Fac_View1 SET FacDept = 'FIN' WHERE FacSalary >

10-16 Multiple Table Updatable Views  No industry standard  Only recently supported  More complex rules than single table updatable views  Access supports flexible view updates for multi-table views  Oracle rules in Appendix 10.B

M Updatable Queries  Associated with 1-M relationships  Join column of the parent table: primary key or unique  Determine updatable tables  Child table updatable  Primary key  Foreign key: must include in the query result  Required columns of the child table  Include primary key and required columns to support insert operations on the parent table  Use join operator style

M Updatable Query Example Example 10: Save as Course_Offering_View1 SELECT Course.CourseNo, CrsDesc, CrsUnits, Offering.OfferNo, OffTerm, OffYear, Offering.CourseNo, OffLocation, OffTime, FacSSN, OffDays FROM Course INNER JOIN Offering ON Course.CourseNo = Offering.CourseNo

10-19 Usage of a 1-M Updatable Query Example 11: Insert a row into the Course_Offering_View1. INSERT INTO Course_Offering_View1 ( OfferNo, Offering.CourseNo, OffTerm, OffYear, OffLocation, OffTime, FacSSN, OffDays ) VALUES ( 7799, 'IS480', 'Spring', 2003, 'BLM201', ' 1:30PM ', ' ', 'MW' )

10-20 Extensions to Multiple Tables  Apply rules to each 1-M relationship  FK of each child table in the query result  Usually only the lowest level child table is updatable  Examples  Course-Offering, Faculty-Offering  Offering-Enrollment, Faculty-Offering

10-21 Hierarchical Forms  Formatted window for data entry and display  Main form  Subform  Provide attractive interface for a 1-M relationship  Specification of data requirements is important

10-22 Revised University Database

10-23 Example Hierarchical Form

10-24 Analysis of Data Requirements  Identify the 1-M relationship  Identify the linking fields  Determine other tables in the main form and the subform  Determine updatable tables  Write queries for the main form and subform

10-25 Registration Form Requirements  1-M relationship: Registration-Enrollment  Linking fields: Registration.RegNo, Enrollment.RegNo  Other tables  Main form: Student  Subform: Offering, Course, Faculty  Updatable tables: Registration, Enrollment

10-26 Registration Main Form Query SELECT RegNo, RegTerm, RegYear, RegDate, Registration.StdSSN, Registration.StdSSN, RegStatus, StdFirstName, StdLastName, StdClass, StdCity, StdState FROM Registration INNER JOIN Student ON Registration.StdSSN = Student.StdSSN

10-27 Registration Subform Query SELECT RegNo, Enrollment.OfferNo, OffTime, Offering.CourseNo, OffLocation, OffTerm, OffYear, Offering.FacSSN, FacFirstName, FacLastName, CrsDesc, CrsUnits FROM ( ( Enrollment INNER JOIN Offering ON Enrollment.OfferNo = Offering.OfferNo ) INNER JOIN Course ON Offering.CourseNo = Course.CourseNo ) LEFT JOIN Faculty ON Faculty.FacSSN = Offering.FacSSN

10-28 Faculty Assignment Form

10-29 Faculty Assignment Requirements  Step 1: Faculty (parent table), Offering (child table)  Step 2: Faculty.FacSSN, Offering.FacSSN  Step 3: Course table in the subform  Step 4: update Offering.FacSSN

10-30 Faculty Assignment Queries  Main form SELECT FacSSN, FacFirstName, FacLastName, FacDept FROM Faculty  Subform SELECT OfferNo, Offering.CourseNo, FacSSN, OffTime, OffDays, OffLocation, CrsUnits FROM Offering INNER JOIN COURSE ON Offering.CourseNo = Course.CourseNo

10-31 Hierarchical Reports  Stylized presentation of data appropriate to a selected audience  Use nesting (or indentation) to provide a visually appealing layout  Vocabulary  Group: sorted field; usually indented  Detail line: innermost field

10-32 Example Hierarchical Report

10-33 Summary Data in Detail Lines

10-34 Query Formulation Skills  Less difficult than skills for forms  Inspect report  Match fields in the report to database columns  Determine the needed tables  Identify the join conditions  Determine the level of detail  Row data versus summary data  Query should provide data for the detail lines

10-35 Faculty Work Load Query SELECT Offering.OfferNo, FacFirstName, FacLastName, FacDept, OffTerm, CrsUnits, OffLimit, Count(Enrollment.RegNo) AS NumStds, NumStds/Offlimit AS PercentFull, (NumStds/Offlimit) < 0.25 AS LowEnrollment FROM Faculty, Offering, Course, Enrollment WHERE Faculty.FacSSN = Offering.FacSSN AND Course.CourseNo = Offering.CourseNo AND Offering.OfferNo = Enrollment.OfferNo AND ( ( Offering.OffTerm = 'Fall' AND Offering.OffYear = 2005 ) OR ( Offering.OffTerm = 'Winter' AND Offering.OffYear = 2006 ) OR ( Offering.OffTerm = 'Spring' AND Offering.OffYear = 2006 ) ) GROUP BY Offering.OfferNo, FacFirstName, FacLastName, FacDept, OffTerm, CrsUnits, OffLimit

10-36 Summary  Significant benefits with a modest performance penalty  Foundation of application data requirements  Updatable views important for hierarchical forms  Carefully analyze data requirements before developing forms and reports

10-37 Questions & Discussion