Defensive Database Programming - Red Gate Software

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Chapter 7: Advanced Use of ConstraintsDeveloperStatus when Justin is activeTicketID DeveloperStatus----------- ---------------1 Active(1 row(s) affected)Listing 7-10: Justin's changed status is propagated to the ticket assigned to him.This automatic propagation of values in the Developer.DeveloperStatuscolumn to the Tickets.DeveloperStatus column, via the cascading update inthe FOREIGN KEY constraint, is the bedrock of this technique. Now, if we attempt toreopen the ticket, by rerunning the UPDATE statement from Listing 7-9, it willsucceed because the DeveloperStatus column for the ticket correctly indicatesthat the developer is active.Continuing our testing, we need to ensure that our developer cannot go on vacation ifany active tickets are assigned to him, as verified by Listing 7-11.UPDATE dbo.DevelopersSET DeveloperStatus = 'Vacation'WHERE DeveloperID = 1 ;Msg 547, Level 16, State 0, Line 1The UPDATE statement conflicted with the CHECK constraint"CHK_Tickets_ValidStatuses". The conflict occurred indatabase "test2", table "dbo.Tickets".The statement has been terminated.Listing 7-11: Justin has an active ticket, so he cannot go on vacation.If we close the ticket, Justin can begin his vacation.BEGIN TRANSACTION ;UPDATE dbo.TicketsSET TicketStatus = 'Closed'218
Chapter 7: Advanced Use of ConstraintsWHERE TicketID = 1 ;UPDATE dbo.DevelopersSET DeveloperStatus = 'Vacation'WHERE DeveloperID = 1 ;-- we shall need the test data intact-- to use in other examples,-- so we roll the changes backROLLBACK ;Listing 7-12: Closing the ticket allows Justin to take a vacation.Alternatively, we can assign the ticket to another developer.BEGIN TRANSACTION ;INSERT INTO dbo.Developers( DeveloperID ,FirstName ,Lastname ,DeveloperStatus)VALUES ( 2 ,'Peter' ,'Yang' ,'Active') ;UPDATE dbo.TicketsSET AssignedToDeveloperID = 2WHERE TicketID = 1 ;UPDATE dbo.DevelopersSET DeveloperStatus = 'Vacation'WHERE DeveloperID = 1 ;219
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Chapter 2: Code Vulnerabilities due
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Enforcing Data Integrity in the App
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About the AuthorAlex Kuznetsov has
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IntroductionResilient T-SQL code is
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IntroductionCh. 02: Code Vulnerabil
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IntroductionSpecific examples demon
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IntroductionWhat this book does not
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Chapter 1: Basic Defensive Database
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Chapter 2: Code Vulnerabilitiesdue
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Chapter 3: Surviving Changes to Dat
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Chapter 4: When Upgrading Breaks Co
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Chapter 5: Reusing T-SQL CodeThe Da
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Chapter 5: Reusing T-SQL CodeIt is
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Chapter 5: Reusing T-SQL CodeAverag
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Chapter 5: Reusing T-SQL CodeBEGINS
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Chapter 5: Reusing T-SQL CodeWe als
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Chapter 5: Reusing T-SQL CodeLet's
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Chapter 5: Reusing T-SQL CodeStateC
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Chapter 5: Reusing T-SQL CodeBEGIN
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Chapter 5: Reusing T-SQL CodeSELECT
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Chapter 5: Reusing T-SQL CodeINSERT
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Chapter 5: Reusing T-SQL CodeUnique
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Chapter 6: Common Problems with Dat
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Chapter 8: Defensive Error Handling
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Defensive Database Programming - Red Gate Software

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