Oracle PLSQL by example, 5th edition

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Oracle®PL/SQLbyExample
FifthEdition
BenjaminRosenzweig
ElenaRakhimov

UpperSaddleRiver,NJ•Boston•Indianapolis•SanFrancisco
NewYork•Toronto•Montreal•London•Munich•Paris•Madrid
Capetown•Sydney•Tokyo•Singapore•MexicoCity

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Rosenzweig,Benjamin.
OraclePL/SQ®byexample/BenjaminRosenzweig,ElenaRakhimov.—Fifthedition.
pagescm
Includesindex.
ISBN978-0-13-379678-0(pbk.:alk.paper)—ISBN0-13-379678-7(pbk.:alk.paper)
1.PL/SQL(Computerprogramlanguage)2.Oracle(Computerfile)3.Relational
databases.
I.Rakhimov,ElenaSilvestrova.II.Title.
QA76.73.P258R682015
005.75’6—
dc232014045792
Copyright©2015PearsonEducation,Inc.

Allrightsreserved.PrintedintheUnitedStatesofAmerica.Thispublicationisprotected
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fortheirloveandsupport
—BenjaminRosenzweig
Tomyfamily,fortheirexcitementandencouragement
—ElenaRakhimov

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Contents
Preface
Acknowledgments
AbouttheAuthors
IntroductiontoPL/SQLNewFeaturesinOracle12c
Invoker’sRightsFunctionsCanBeResult-Cached

MorePL/SQL-OnlyDataTypesCanCrossthePL/SQL-to-SQLInterface
Clause
ACCESSIBLEBYClause
FETCHFIRSTClause
RolesCanBeGrantedtoPL/SQLPackagesandStand-AloneSubprograms
MoreDataTypesHavetheSameMaximumSizeinSQLandPL/SQL
DatabaseTriggersonPluggableDatabases
LIBRARYCanBeDefinedasaDIRECTORYObjectandwitha
CREDENTIALClause
ImplicitStatementResults
BEQUEATHCURRENT_USERViews
INHERITPRIVILEGESandINHERITANYPRIVILEGESPrivileges
InvisibleColumns
Objects,NotTypes,AreEditionedorNoneditioned
PL/SQLFunctionsThatRunFasterinSQL
PredefinedInquiryDirectives$$PLSQL_UNIT_OWNERand
$$PLSQL_UNIT_TYPE
CompilationParameterPLSQL_DEBUGIsDeprecated
Chapter1PL/SQLConcepts
Lab1.1:PL/SQLArchitecture
PL/SQLArchitecture
PL/SQLBlockStructure
HowPL/SQLGetsExecuted
Lab1.2:PL/SQLDevelopmentEnvironment
GettingStartedwithSQLDeveloper
GettingStartedwithSQL*Plus
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Lab1.3:PL/SQL:TheBasics

DBMS_OUTPUT.PUT_LINEStatement
SubstitutionVariableFeature
Summary
Chapter2PL/SQLLanguageFundamentals
Lab2.1:PL/SQLProgrammingFundamentals
PL/SQLLanguageComponents
PL/SQLVariables
PL/SQLReservedWords
IdentifiersinPL/SQL
AnchoredDataTypes
DeclareandInitializeVariables
ScopeofaBlock,NestedBlocks,andLabels
Summary
Chapter3SQLinPL/SQL
Lab3.1:DMLStatementsinPL/SQL
InitializeVariableswithSELECTINTO
UsingtheSELECTINTOSyntaxforVariableInitialization
UsingDMLinaPL/SQLBlock
UsingaSequenceinaPL/SQLBlock
Lab3.2:TransactionControlinPL/SQL
UsingCOMMIT,ROLLBACK,andSAVEPOINT
PuttingTogetherDMLandTransactionControl
Summary
Chapter4ConditionalControl:IFStatements
Lab4.1:IFStatements
IF-THENStatements
IF-THEN-ELSEStatement
Lab4.2:ELSIFStatements
Lab4.3:NestedIFStatements
Summary

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Lab5.1:CASEStatements
CASEStatements
SearchedCASEStatements
Lab5.2:CASEExpressions
Lab5.3:NULLIFandCOALESCEFunctions
NULLIFFunction
COALESCEFunction
Summary
Chapter6IterativeControl:PartI
Lab6.1:SimpleLoops
EXITStatement
EXITWHENStatement
Lab6.2:WHILELoops
UsingWHILELoops
PrematureTerminationoftheWHILELoop
Lab6.3:NumericFORLoops
UsingtheINOptionintheLoop
UsingtheREVERSEOptionintheLoop
PrematureTerminationoftheNumericFORLoop
Summary
Chapter7IterativeControl:PartII
Lab7.1:CONTINUEStatement
UsingCONTINUEStatement
CONTINUEWHENStatement
Lab7.2:NestedLoops
UsingNestedLoops
UsingLoopLabels

Summary
Chapter8ErrorHandlingandBuilt-inExceptions
Lab8.1:HandlingErrors
Lab8.2:Built-inExceptions
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Chapter9Exceptions
Lab9.1:ExceptionScope
Lab9.2:User-DefinedExceptions
Lab9.3:ExceptionPropagation
Re-raisingExceptions
Summary
Chapter10Exceptions:AdvancedConcepts
Lab10.1:RAISE_APPLICATION_ERROR
Lab10.2:EXCEPTION_INITPragma
Lab10.3:SQLCODEandSQLERRM
Summary
Chapter11IntroductiontoCursors
Lab11.1:TypesofCursors
MakingUseofanImplicitCursor
MakingUseofanExplicitCursor
Lab11.2:CursorLoop
ProcessinganExplicitCursor
MakingUseofaUser-DefinedRecord
MakingUseofCursorAttributes
Lab11.3:CursorFORLOOPs
MakingUseofCursorFORLOOPs
Lab11.4:NestedCursors
ProcessingNestedCursors

Summary
Chapter12AdvancedCursors
Lab12.1:ParameterizedCursors
CursorswithParameters
Lab12.2:ComplexNestedCursors
Lab12.3:FORUPDATEandWHERECURRENTCursors
FORUPDATECursor
FORUPDATEOFinaCursor
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Summary
Chapter13Triggers
Lab13.1:WhatTriggersAre
DatabaseTrigger
BEFORETriggers
AFTERTriggers
AutonomousTransaction
Lab13.2:TypesofTriggers
RowandStatementTriggers
INSTEADOFTriggers
Summary
Chapter14MutatingTablesandCompoundTriggers
Lab14.1:MutatingTables
WhatIsaMutatingTable?
ResolvingMutatingTableIssues
Lab14.2:CompoundTriggers
WhatIsaCompoundTrigger?
ResolvingMutatingTableIssueswithCompoundTriggers
Summary

Chapter15Collections
Lab15.1:PL/SQLTables
AssociativeArrays
NestedTables
CollectionMethods
Lab15.2:Varrays
Lab15.3:MultilevelCollections
Summary
Chapter16Records
Lab16.1:RecordTypes
Table-BasedandCursor-BasedRecords
User-DefinedRecords

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Lab16.2:NestedRecords
Lab16.3:CollectionsofRecords
Summary
Chapter17NativeDynamicSQL
Lab17.1:EXECUTEIMMEDIATEStatements
UsingtheEXECUTEIMMEDIATEStatement
HowtoAvoidCommonORAErrorsWhenUsingEXECUTE
IMMEDIATE
Lab17.2:OPEN-FOR,FETCH,andCLOSEStatements
OpeningCursor
FetchingfromaCursor
ClosingaCursor
Summary
Chapter18BulkSQL

Lab18.1:FORALLStatements
UsingFORALLStatements
SAVEEXCEPTIONSOption
INDICESOFOption
VALUESOFOption
Lab18.2:TheBULKCOLLECTClause
Lab18.3:BindingCollectionsinSQLStatements
BindingCollectionswithEXECUTEIMMEDIATEStatements
BindingCollectionswithOPEN-FOR,FETCH,andCLOSEStatements
Summary
Chapter19Procedures
BenefitsofModularCode
BlockStructure
AnonymousBlocks
Lab19.1:CreatingProcedures
PuttingProcedureCreationSyntaxintoPractice
QueryingtheDataDictionaryforInformationonProcedures


UsingINandOUTParameterswithProcedures
Summary
Chapter20Functions
Lab20.1:CreatingFunctions
CreatingStoredFunctions
MakingUseofFunctions
Lab20.2:UsingFunctionsinSQLStatements
InvokingFunctionsinSQLStatements
WritingComplexFunctions
Lab20.3:OptimizingFunctionExecutioninSQL
DefiningaFunctionUsingtheWITHClause

CreatingaFunctionwiththeUDFPragma
Summary
Chapter21Packages
Lab21.1:CreatingPackages
CreatingPackageSpecifications
CreatingPackageBodies
CallingStoredPackages
CreatingPrivateObjects
Lab21.2:CursorVariables
Lab21.3:ExtendingthePackage
ExtendingthePackagewithAdditionalProcedures
Lab21.4:PackageInstantiationandInitialization
CreatingPackageVariablesDuringInitialization
Lab21.5:SERIALLY_REUSABLEPackages
UsingtheSERIALLY_REUSABLEPragma
Summary
Chapter22StoredCode
Lab22.1:GatheringInformationaboutStoredCode
GettingStoredCodeInformationfromtheDataDictionary
OverloadingModules


Chapter23ObjectTypesinOracle
Lab23.1:ObjectTypes
CreatingObjectTypes
UsingObjectTypeswithCollections
Lab23.2:ObjectTypeMethods
ConstructorMethods
MemberMethods
StaticMethods

ComparingObjects
Summary
Chapter24Oracle-SuppliedPackages
Lab24.1:ExtendingFunctionalitywithOracle-SuppliedPackages
AccessingFileswithinPL/SQLwithUTL_FILE
SchedulingJobswithDBMS_JOB
GeneratinganExplainPlanwithDBMS_XPLAN
GeneratingImplicitStatementResultswithDBMS_SQL
Lab24.2:ErrorReportingwithOracle-SuppliedPackages
UsingtheDBMS_UTILITYPackageforErrorReporting
UsingtheUTL_CALL_STACKPackageforErrorReporting
Summary
Chapter25OptimizingPL/SQL
Lab25.1:PL/SQLTuningTools
PL/SQLProfilerAPI
TraceAPI
PL/SQLHierarchicalProfiler
Lab25.2:PL/SQLOptimizationLevels
Lab25.3:SubprogramInlining
Summary
AppendixAPL/SQLFormattingGuide
Case
WhiteSpace


Comments
OtherSuggestions
AppendixBStudentDatabaseSchema
TableandColumnDescriptions
Index

Preface
Oracle®PL/SQLbyExample,FifthEdition,presentstheOraclePL/SQLprogramming
languageinauniqueandhighlyeffectiveformat.ItchallengesyoutolearnOracle
PL/SQLbyusingitratherthanbysimplyreadingaboutit.
Justasagrammarworkbookwouldteachyouaboutnounsandverbsbyfirstshowing
youexamplesandthenaskingyoutowritesentences,Oracle®PL/SQLbyExample
teachesyouaboutcursors,loops,procedures,triggers,andsoonbyfirstshowingyou
examplesandthenaskingyoutocreatetheseobjectsyourself.

WhoThisBookIsFor
Thisbookisintendedforanyonewhoneedsaquickbutdetailedintroductionto
programmingwithOracle’sPL/SQLlanguage.Theidealreadersarethosewithsome
relationaldatabaseexperience,withsomeOracleexperience,specificallywithSQL,
SQL*Plus,andSQLDeveloper,butwithlittleornoexperiencewithPL/SQLorwithmost
otherprogramminglanguages.
Thecontentofthisbookisbasedprimarilyonthematerialthatwastaughtinan
IntroductiontoPL/SQLclassatColumbiaUniversity’sComputerTechnologyand
Applications(CTA)programinNewYorkCity.Thestudentbodywasratherdiverse,in
thatthereweresomestudentswhohadyearsofexperiencewithinformationtechnology
(IT)andprogramming,butnoexperiencewithOraclePL/SQL,andthentherewerethose
withabsolutelynoexperienceinITorprogramming.Thecontentofthebook,likethe
class,isbalancedtomeettheneedsofbothextremes.Theadditionalexercisesavailable
throughthecompanionwebsitecanbeusedaslabsandhomeworkassignmentsto
accompanythelecturesinsuchaPL/SQLcourse.

HowThisBookIsOrganized
TheintentofthisworkbookistoteachyouaboutOraclePL/SQLbyexplaininga
programmingconceptoraparticularPL/SQLfeatureandthenillustrateitfurtherby

meansofexamples.Oftentimes,asthetopicisdiscussedmoreindepth,theseexamples
wouldbechangedtoillustratenewlycoveredmaterial.Inaddition,mostofthechaptersof
thisbookhaveAdditionalExercisessectionsavailablethroughthecompanionwebsite.
Theseexercisesallowyoutotestthedepthofyourunderstandingofthenewmaterial.
Thebasicstructureofeachchapterisasfollows:
Objectives
Introduction
Lab
Lab…
Summary
TheObjectivessectionliststopicscoveredinthechapter.Basicallyasingleobjective
correspondstoasingleLab.


chapter.
EachLabcoversasingleobjectivelistedintheObjectivessectionofthechapter.In
someinstancestheobjectiveisdividedevenfurtherintothesmallerindividualtopicsin
theLab.Theneachsuchtopicisexplainedandillustratedwiththehelpofexamplesand
correspondingoutputs.Notethatasmuchaspossible,eachexampleisprovidedinits
entiretysothatacompletecodesampleisreadilyavailable.
AttheendofeachchapteryouwillfindaSummarysection,whichprovidesabrief
conclusionofthematerialdiscussedinthechapter.Inaddition,theBytheWayportion
willstatewhetheraparticularchapterhasanAdditionalExercisessectionavailableonthe
companionwebsite.

AbouttheCompanionWebsite
ThecompanionWebsiteislocatedatinformit.com/title/0133796787.Hereyouwillfind
threeveryimportantthings:
FilesrequiredtocreateandinstalltheSTUDENTschema.
Filesthatcontainexamplescriptsusedinthebookchapters.

AdditionalExerciseschapters,whichhavetwoparts:
•AQuestionsandAnswerspartwhereyouareaskedaboutthematerialpresented
inaparticularchapteralongwithsuggestedanswerstothesequestions.
Oftentimes,youareaskedtomodifyascriptbasedonsomerequirementsand
explainthedifferenceintheoutputcausedbythesemodifications.Notethatthis
partisalsoorganizedintoLabssimilartoitscorrespondingchapterinthebook.
•ATryitYourselfpartwhereyouareaskedtocreatescriptsbasedonthe
requirementsprovided.ThispartisdifferentfromtheQuestionsandAnswerspart
inthattherearenoscriptssuppliedwiththequestions.Instead,youwillneedto
createscriptsintheirentirety.
BytheWay
Youneedtovisitthecompanionwebsite,downloadthestudentschema,and
installitinyourdatabasepriortousingthisbookifyouwouldliketheability
toexecutethescriptsprovidedinthechaptersandonthesite.

WhatYouWillNeed
Therearesoftwareprogramsaswellasknowledgerequirementsnecessarytocompletethe
Labsinthisbook.Notethatsomefeaturescoveredthroughoutthebookareapplicableto
Oracle12conly.However,youwillbeabletorunagreatmajorityoftheexamplesand
completeAdditionalExercisesandTryitYourselfsectionsbyusingthefollowing
products:
Oracle11gorhigher


AccesstotheInternet
YoucanuseeitherOraclePersonalEditionorOracleEnterpriseEditiontoexecutethe
examplesinthisbook.IfyouuseOracleEnterpriseEdition,itcanberunningonaremote
serverorlocallyonyourownmachine.ItisrecommendedthatyouuseOracle11gor
Oracle12cinordertoperformalloramajorityoftheexamplesinthisbook.Whena
featurewillonlyworkinthelatestversionofOracledatabase,thebookwillstateso

explicitly.Additionally,youshouldhaveaccesstoandbefamiliarwithSQLDeveloperor
SQL*Plus.
YouhaveanumberofoptionsforhowtoeditandrunscriptsinSQLDeveloperorfrom
SQL*Plus.Therearealsomanythird-partyprogramstoeditanddebugPL/SQLcode.
Both,SQLDeveloperandSQL*Plusareusedthroughoutthisbook,sincethesearetwo
Oracle-providedtoolsandcomeaspartoftheOracleinstallation.
BytheWay
Chapter1hasaLabtitledPL/SQLDevelopmentEnvironmentthatdescribes
howtogetstartedwithSQLDeveloperandSQL*Plus.However,agreat
majorityoftheexamplesusedinthebookwereexecutedinSQLDeveloper.

AbouttheSampleSchema
TheSTUDENTschemacontainstablesandotherobjectsmeanttokeepinformationabout
aregistrationandenrollmentsystemforafictitiousuniversity.Therearetentablesinthe
systemthatstoredataaboutstudents,courses,instructors,andsoon.Inadditiontostoring
contactinformation(addressesandtelephonenumbers)forstudentsandinstructors,and
descriptiveinformationaboutcourses(costsandprerequisites),theschemaalsokeeps
trackofthesectionsforparticularcourses,andthesectionsinwhichstudentshave
enrolled.
TheSECTIONtableisoneofthemostimportanttablesintheschemabecauseitstores
dataabouttheindividualsectionsthathavebeencreatedforeachcourse.Eachsection
recordalsostoresinformationaboutwhereandwhenthesectionwillmeetandwhich
instructorwillteachthesection.TheSECTIONtableisrelatedtotheCOURSEand
INSTRUCTORtables.
TheENROLLMENTtableisequallyimportantbecauseitkeepstrackofwhichstudents
haveenrolledinwhichsections.Eachenrollmentrecordalsostoresinformationaboutthe
student’sgradeandenrollmentdate.TheenrollmenttableisrelatedtotheSTUDENTand
SECTIONtables.
TheSTUDENTschemaalsohasanumberofothertablesthatmanagegradingforeach
studentineachsection.

ThedetailedstructureoftheSTUDENTschemaisdescribedinAppendixB,Student
DatabaseSchema.


Acknowledgments
BenRosenzweig:IwouldliketothankmycoauthorElenaRakhimovforbeinga
wonderfulandknowledgeablecolleaguetoworkwith.IwouldalsoliketothankDouglas
Schererforgivingmetheopportunitytoworkonthisbookaswellasforproviding
constantsupportandassistancethroughtheentirewritingprocess.Iamindebtedtothe
teamatPrenticeHall,whichincludesGregDoench,MichelleHousley,andespecially
SonglinQiuforherdetailededits.Finally,Iwouldliketothankthemanyfriendsand
family,especiallyEdwardClarinandEdwardKnopping,forhelpingmethroughthelong
processofputtingthewholebooktogether,whichincludedmanylatenightsand
weekends.
ElenaRakhimov:Mycontributiontothisbookreflectsthehelpandadviceofmany
people.IamparticularlyindebtedtomycoauthorBenRosenzweigformakingthisproject
arewardingandenjoyableexperience.ManythankstoGregDoench,MichelleHousley,
andespeciallySonglinQiuforhermeticulouseditingskills,andmanyothersatPrentice
Hallwhodiligentlyworkedtobringthisbooktomarket.ThankstoMichaelRinomhota
forhisinvaluableexpertiseinsettinguptheOracleenvironmentandDanHotkaforhis
valuablecommentsandsuggestions.Mostimportantly,tomyfamily,whoseexcitement,
enthusiasm,inspiration,andsupportencouragedmetoworkhardtotheveryend,and
wereexceededonlybytheirlove.


AbouttheAuthors
BenjaminRosenzweigisaSeniorProjectManageratMisysFinancialSoftware,where
hehasworkedsince2002.Priortothathewasaprincipalconsultantformorethanthree
yearsatOracleCorporationintheCustomDevelopmentDepartment.Hiscomputer
experiencerangesfromcreatinganelectronicTibetan–EnglishDictionaryinKathmandu,

Nepal,tosupportingpresentationcentersatGoldmanSachsandmanagingatrading
systematTIAA-CREF.BenjaminhasbeenaninstructorattheColumbiaUniversity
ComputerTechnologyandApplicationprograminNewYorkCitysince1998.In2002he
wasawardedthe“OutstandingTeachingAward”fromtheChairandDirectoroftheCTA
program.HeholdsaB.A.fromReedCollegeandacertificateindatabasedevelopment
anddesignfromColumbiaUniversity.HispreviousbookswithPrenticeHallareOracle
FormsDeveloper:TheCompleteVideoCourse(2000),andOracleWebApplication
ProgrammingforPL/SQLDevelopers(2003).
ElenaRakhimovhasover20yearsofexperienceindatabasearchitectureand
developmentinawidespectrumofenterpriseandbusinessenvironmentsrangingfrom
non-profitorganizationstoWallStreettohercurrentpositionwithaprominentsoftware
companywheresheheadsupthedatabaseteam.Herdeterminationtostay“hands-on”
notwithstanding,Elenamanagedtoexcelintheacademicarenahavingtaughtrelational
databaseprogrammingatColumbiaUniversity’shighlyesteemedComputerTechnology
andApplicationsprogram.ShewaseducatedindatabaseanalysisanddesignatColumbia
UniversityandinappliedmathematicsatBakuStateUniversityinAzerbaijan.She
currentlyresidesinVancouver,Canada.


IntroductiontoPL/SQLNewFeaturesinOracle
12c
Oracle12chasintroducedanumberofnewfeaturesandimprovementsforPL/SQL.This
introductionbrieflydescribesfeaturesnotcoveredinthisbookandpointsyoutospecific
chaptersforfeaturesthatarewithinthescopeofthisbook.Thelistoffeaturesdescribed
hereisalsoavailableinthe“ChangesinThisReleaseforOracleDatabasePL/SQL
LanguageReference”sectionofthePL/SQLLanguageReferencemanualofferedaspart
ofOracle’sonlinehelp.
ThenewPL/SQLfeaturesandenhancementsareasfollows:
Invoker’srightsfunctionscanberesult-cached
MorePL/SQL-onlydatatypescancrossthePL/SQL-to-SQLinterfaceclause

ACCESSIBLEBYclause
FETCHFIRSTclause
RolescanbegrantedtoPL/SQLpackagesandstand-alonesubprograms
MoredatatypeshavethesamemaximumsizeinSQLandPL/SQL
Databasetriggersonpluggabledatabases
LIBRARYcanbedefinedasDIRECTORYobjectandwithCREDENTIALclause
Implicitstatementresults
BEQUEATHCURRENT_USERviews
INHERITPRIVILEGESandINHERITANYPRIVILEGESprivileges
Invisiblecolumns
Objects,nottypes,areeditionedornoneditioned
PL/SQLfunctionsthatrunfasterinSQL
Predefinedinquirydirectives$$PLSQL_UNIT_OWNERand
$$PLSQL_UNIT_TYPE
CompilationparameterPLSQL_DEBUGisdeprecated

Invoker’sRightsFunctionsCanBeResult-Cached
WhenastoredsubprogramiscreatedinOracleproducts,itmaybecreatedaseithera
definerrights(DR)unitoraninvokerrights(IR)unit.ADRunitwouldexecutewiththe
permissionsofitsowner,whereasanIRunitwouldexecutewiththepermissionsofauser
whoinvokedthatparticularunit.Bydefault,astoredsubprogramiscreatedasaDRunit
unlessexplicitlyspecifiedotherwise.WhetheraparticularunitisconsideredaDRorIR
unitiscontrolledbytheAUTHIDproperty,whichmaybesettoeitherDEFINER(default)
orCURRENT_USER.
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CURRENT_USER)couldnotberesult-cached.TocreateafunctionasanIRunit,the
AUTHIDclausemustbeaddedtothefunctionspecification.
Aresult-cachedfunctionisafunctionwhoseparametervaluesandresultarestoredin

thecache.Asaconsequence,whensuchafunctionisinvokedwiththesameparameter
values,itsresultisretrievedfromthecacheinsteadofbeingcomputedagain.Toenablea
functionforresult-caching,theRESULT_CACHEclausemustbeaddedtothefunction
specification.Thisisdemonstratedbythefollowingexample(theinvokerrightsclause
andresult-cachingarehighlightedinbold).
ForExampleResult-CachingFunctionsCreatedwithInvoker’sRights
Clickheretoviewcodeimage
CREATEORREPLACEFUNCTIONget_student_rec(p_student_idINNUMBER)
RETURNSTUDENT%ROWTYPE
AUTHIDCURRENT_USER
RESULT_CACHERELIES_ON(student)
IS
v_student_recSTUDENT%ROWTYPE;
BEGIN
SELECT*
INTOv_student_rec
FROMstudent
WHEREstudent_id=p_student_id;
RETURNv_student_rec;
EXCEPTION
WHENno_data_found
THEN
RETURNNULL;
ENDget_student_rec;
/
—Executenewlycreatedfunction
DECLARE
v_student_recSTUDENT%ROWTYPE;
BEGIN
v_student_rec:=get_student_rec(p_student_id=>230);

END;

NotethatifthestudentrecordforstudentID230isintheresultcachealready,thenthe
functionwillreturnthestudentrecordfromtheresultcache.Intheoppositecase,the
studentrecordwillbeselectedfromtheSTUDENTtableandaddedtothecacheforfuture
use.BecausetheresultcacheofthefunctionreliesontheSTUDENTtable,anychanges
appliedandcommittedontheSTUDENTtablewillinvalidateallcachedresultsforthe
get_student_recfunction.


MorePL/SQL-OnlyDataTypesCanCrossthePL/SQL-toSQLInterfaceClause
Inthisrelease,OraclehasextendedsupportofPL/SQL-onlydatatypestodynamicSQL
andclientprograms(OCIorJDBC).Forexample,youcanbindcollectionsvariables
whenusingtheEXECUTEIMMEDIATEstatementortheOPENFOR,FETCH,and
CLOSEstatements.ThistopiciscoveredingreaterdetailinLab18.3,BindingCollections
inSQLStatements,inChapter18.

ACCESSIBLEBYClause
AnoptionalACCESSIBLEBYclauseenablesyoutospecifyalistofPL/SQLunitsthat
mayaccessthePL/SQLunitbeingcreatedormodified.TheACCESSIBLEBYclauseis
typicallyaddedtothemoduleheader—forexample,tothefunctionorprocedureheader.
EachunitlistedintheACCESSIBLEBYclauseiscalledanaccessor,andtheclause
itselfisalsocalledawhitelist.Thisisdemonstratedinthefollowingexample(the
ACCESSIBLEBYclauseisshowninbold).
ForExampleProcedureCreatedwiththeACCESSIBLEBYClause
Clickheretoviewcodeimage
CREATEORREPLACEPROCEDUREtest_proc1
ACCESSIBLEBY(TEST_PROC2)
AS
BEGIN

DBMS_OUTPUT.PUT_LINE(‘TEST_PROC1’);
ENDtest_proc1;
/
CREATEORREPLACEPROCEDUREtest_proc2
AS
BEGIN
DBMS_OUTPUT.PUT_LINE(‘TEST_PROC2’);
test_proc1;
ENDtest_proc2;
/
—ExecuteTEST_PROC2
BEGIN
test_proc2;
END;
/
TEST_PROC2
TEST_PROC1
—ExecuteTEST_PROC1directly
BEGIN
test_proc1;
END;
/
ORA-06550:line2,column4:
PLS-00904:insufficientprivilegetoaccessobjectTEST_PROC1
ORA-06550:line2,column4:


Inthisexample,therearetwoprocedures,test_proc1andtest_proc2,and
test_proc1iscreatedwiththeACCESSIBLEBYclause.Asaconsequence,
test_proc1maybeaccessedbytest_proc2only.Thisisdemonstratedbytwo

anonymousPL/SQLblocks.Thefirstblockexecutestest_proc2successfully.The
secondblockattemptstoexecutetest_proc1directlyand,asaresult,causesanerror.
Notethatbothprocedureswerecreatedwithinasingleschema(STUDENT),andthat
bothPL/SQLblockswereexecutedinthesinglesessionbytheschemaowner
(STUDENT).

FETCHFIRSTClause
TheFETCHFIRSTclauseisanewoptionalfeaturethatistypicallyusedwiththe“TopN”queriesasillustratedbythefollowingexample.TheENROLLMENTtableusedinthis
examplecontainsstudentregistrationdata.Eachstudentisidentifiedbyauniquestudent
IDandmayberegisteredformultiplecourses.TheFETCHFIRSTclauseisshownin
bold.
ForExampleUsingFETCHFIRSTClausewith“Top-N”Query
Clickheretoviewcodeimage
—SamplestudentIDsfromtheENROLLMENTtable
SELECTstudent_id
FROMenrollment;
STUDENT_ID
–––102
102
103
104
105
106
106
107
108
109
109
110
110

…
—“Top-N”queryreturnsstudentIDsforthe5studentsthatregisteredfor
themost
—courses
SELECTstudent_id,COUNT(*)courses
FROMenrollment
GROUPBYstudent_id
ORDERBYcoursesdesc
FETCHFIRST5ROWSONLY;
STUDENT_IDCOURSES
–––-––-


1244
2323
2153
1843

NotethatFETCHFIRSTclausemayalsobeusedinconjunctionwiththeBULK
COLLECTINTOclauseasdemonstratedhere.TheFETCHFIRSTclauseisshownin
bold.
ForExampleUsingFETCHFIRSTClausewithBULKCOLLECTINTOClause
Clickheretoviewcodeimage
DECLARE
TYPEstudent_name_tabISTABLEOFVARCHAR2(100)INDEXBYPLS_INTEGER;
student_namesstudent_name_tab;
BEGIN
—Fetchingfirst20studentnamesonly
SELECTfirst_name||’‘||last_name
BULKCOLLECTINTOstudent_names

FROMstudent
FETCHFIRST20ROWSONLY;
DBMS_OUTPUT.PUT_LINE(‘Thereare‘||student_names.COUNT||’students’);
END;
/
Thereare20students

RolesCanBeGrantedtoPL/SQLPackagesandStandAloneSubprograms
StartingwithOracle12c,youareabletograntrolestoPL/SQLpackagesandstand-alone
subprograms.NotethatgrantingaroletoaPL/SQLpackageorstand-alonesubprogram
doesnotalteritscompilation.Instead,itaffectshowprivilegesrequiredbytheSQL
statementsthatareissuedbythePL/SQLunitatruntimearechecked.
ConsiderthefollowingexamplewheretheREADroleisgrantedtothefunction
get_student_name.
ForExampleGrantingREADRoletotheget_student_nameFunction
Clickheretoviewcodeimage
GRANTREADTOFUNCTIONget_student_name;


MoreDataTypesHavetheSameMaximumSizeinSQLand
PL/SQL
PriortoOracle12c,somedatatypeshaddifferentmaximumsizesinSQLandinPL/SQL.
Forexample,inSQLthemaximumsizeofNVARCHAR2was4000bytes,whereasin
PL/SQLitwas32,767bytes.StartingwithOracle12c,themaximumsizesofthe
VARCHAR2,NVARCHAR2,andRAWdatatypeshavebeenextendedto32,767forboth
SQLandPL/SQL.ToseethesemaximumsizesinSQL,theinitializationparameter
MAX_STRING_SIZEmustbesettoEXTENDED.

DatabaseTriggersonPluggableDatabases
Thepluggabledatabase(PDB)isoneofthecomponentsofOracle’smultitenant

architecture.Typicallyitisaportablecollectionofschemasandotherdatabaseobjects.
StartingwithOracle12c,youareabletocreateeventtriggersonPDBs.Detailed
informationontriggersisprovidedinChapters13and14.NotethatPDBsareoutsidethe
scopeofthisbook,butdetailedinformationonthemmaybefoundinOracle’sonline
AdministrationGuide.

LIBRARYCanBeDefinedasaDIRECTORYObjectandwith
aCREDENTIALClause
ALIBRARYisaschemaobjectassociatedwithasharedlibraryofanoperatingsystem.It
iscreatedwiththehelpoftheCREATEORREPLACELIBRARYstatement.A
DIRECTORYisalsoanobjectthatmapsanaliastoanactualdirectoryontheserverfile
system.TheDIRECTORYobjectiscoveredverybrieflyinChapter25aspartoftheinstall
processesforthePL/SQLProfilerAPIandPL/SQLHierarchicalProfiler.IntheOracle
12crelease,aLIBRARYobjectmaybedefinedasaDIRECTORYobjectwithanoptional
CREDENTIALclauseasshownhere.
ForExampleCreatingLIBRARYasDIRECTORYObject
Clickheretoviewcodeimage
CREATEORREPLACELIBRARYmy_libAS‘plsql_code’INmy_dir;

Inthisexample,theLIBRARYobjectmy_libiscreatedasaDIRECTORYobject.The
'plsql_code'isthenameofthedynamiclinklibrary(DDL)intheDIRECTORY
objectmy_dir.Notethatforthislibrarytobecreatedsuccessfully,theDIRECTORY
objectmy_dirmustbecreatedbeforehand.MoreinformationonLIBRARYand
DIRECTORYobjectscanbefoundinOracle’sonlineDatabasePL/SQLLanguage
Reference.