Tutorial: Database Communication in LabVIEW

UniversityCollegeofSoutheastNorway

http://home.hit.no/~hansha

DatabaseCommunication inLabVIEW

Hans-PetterHalvorsen,2016.10.31

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PrefaceThisdocumentexplainsthebasicconceptsofadatabasesystemandhowtocommunicatewithadatabasefromLabVIEW.

YoushouldhavesomebasicknowledgeaboutLabVIEW,e.g.,the“AnIntroductiontoLabVIEW”training.Thisdocumentisavailablefordownloadathttp://home.hit.no/~hansha/.

InadditiontoLabVIEWProfessionalDevelopmentSystem,youneedtoinstallthe“LabVIEWDatabaseConnectivityToolkit”.

FormoreinformationaboutLabVIEWandDatabases,visitmyBlog:http://home.hit.no/~hansha/

Sometextinthisdocumentisbasedontextfromwww.wikipedia.organd“LabVIEWDatabaseConnectivityToolkitUserManual”.

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TableofContentsPreface......................................................................................................................................2

TableofContents.....................................................................................................................iii

1 IntroductiontoLabVIEW...................................................................................................1

1.1 Dataflowprogramming...............................................................................................1

1.2 Graphicalprogramming..............................................................................................1

1.3 Benefits.......................................................................................................................2

2 DatabaseSystems.............................................................................................................3

2.1 RDBMSComponents...................................................................................................3

2.2 Datawarehouse..........................................................................................................4

2.3 RelationalDatabase....................................................................................................4

2.4 Real-timedatabases...................................................................................................4

2.5 DatabaseManagementSystems................................................................................5

2.6 MDAC..........................................................................................................................5

2.6.1 ODBC...................................................................................................................5

2.6.2 OLEDB.................................................................................................................6

2.6.3 ADO(ActiveXDataObjects).................................................................................6

3 RelationalDatabases.........................................................................................................7

3.1 Tables..........................................................................................................................7

3.2 UniqueKeysandPrimaryKey.....................................................................................7

3.3 ForeignKey.................................................................................................................9

3.4 Views........................................................................................................................10

3.5 Functions..................................................................................................................10

iv TableofContents

Tutorial: Database Communication in LabVIEW

3.6 Storedprocedures....................................................................................................11

3.7 Triggers.....................................................................................................................11

4 StructuredQueryLanguage(SQL)...................................................................................13

4.1 Queries.....................................................................................................................13

4.2 Datamanipulation....................................................................................................14

4.3 Datadefinition..........................................................................................................15

4.4 Datatypes.................................................................................................................16

4.4.1 Characterstrings...............................................................................................16

4.4.2 Bitstrings...........................................................................................................16

4.4.3 Numbers............................................................................................................16

4.4.4 DateandTime...................................................................................................16

5 DatabaseModelling........................................................................................................17

5.1 ERDiagram...............................................................................................................17

5.2 MicrosoftVisio..........................................................................................................18

5.3 EXERCISES.....................................................................Error!Bookmarknotdefined.

6 MicrosoftSQLServer.......................................................................................................21

6.1 Introduction..............................................................................................................21

6.2 Requirements...........................................................................................................21

6.3 SQLServerExpress....................................................................................................21

6.4 AdventureWorks.......................................................................................................22

6.5 SQLServerManagementStudio...............................................................................22

6.6 CreateanewDatabase.............................................................................................23

6.7 Backup/Restore........................................................................................................24

6.8 ExampleDatabase....................................................................................................25

6.9 Exercises...................................................................................................................27

7 MicrosoftOfficeAccess...................................................................................................28

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7.1 Introduction..............................................................................................................28

7.2 ExampleDatabase....................................................................................................28

7.3 Exercises...................................................................................................................30

8 ODBC...............................................................................................................................32

8.1 WhatisODBC?..........................................................................................................32

8.2 CreateanODBCConnectionin“ODBCDataSourceAdministrator”........................32

8.3 GetdataintoExcelusingyourODBCConnection.....................................................34

9 LabVIEWDatabaseConnectivityToolkit.........................................................................38

9.1 ConnecttotheDatabase..........................................................................................39

9.1.1 DSN....................................................................................................................40

9.1.2 UDL....................................................................................................................41

9.1.3 ConnectionString..............................................................................................42

9.2 ReadingDatafromtheDatabase..............................................................................42

9.3 WritingDatatotheDatabase...................................................................................46

9.4 CreatingandDroppingTables..................................................................................48

9.5 UsingtheDatabaseConnectivityToolkitUtilityVIs..................................................49

9.6 PerformingAdvancedDatabaseOperations............................................................50

10 CreatingandUsingTables...............................................................................................52

10.1 Exercises...................................................................................................................55

11 CreatingandUsingViews................................................................................................56

11.1 Exercises...................................................................................................................59

12 CreatingandusingStoredProcedures............................................................................60

12.1 Exercises...................................................................................................................62

13 CreatingandUsingTriggers............................................................................................63

13.1 Exercises...................................................................................................................66

14 CreatingandusingFunctions..........................................................................................67

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14.1 Exercises...................................................................................................................67

15 SQLToolkit......................................................................................................................68

15.1 Installation................................................................................................................68

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1 IntroductiontoLabVIEWLabVIEW(shortforLaboratoryVirtualInstrumentationEngineeringWorkbench)isaplatformanddevelopmentenvironmentforavisualprogramminglanguagefromNationalInstruments.Thegraphicallanguageisnamed"G".OriginallyreleasedfortheAppleMacintoshin1986,LabVIEWiscommonlyusedfordataacquisition,instrumentcontrol,andindustrialautomationonavarietyofplatformsincludingMicrosoftWindows,variousflavorsofUNIX,Linux,andMacOSX.ThelatestversionofLabVIEWisversionLabVIEW2009,releasedinAugust2009.VisitNationalInstrumentsatwww.ni.com.

Thecodefileshavetheextension“.vi”,whichisaabbreviationfor“VirtualInstrument”.LabVIEWofferslotsofadditionalAdd-OnsandToolkits.

1.1 DataflowprogrammingTheprogramminglanguageusedinLabVIEW,alsoreferredtoasG,isadataflowprogramminglanguage.Executionisdeterminedbythestructureofagraphicalblockdiagram(theLV-sourcecode)onwhichtheprogrammerconnectsdifferentfunction-nodesbydrawingwires.Thesewirespropagatevariablesandanynodecanexecuteassoonasallitsinputdatabecomeavailable.Sincethismightbethecaseformultiplenodessimultaneously,Gisinherentlycapableofparallelexecution.Multi-processingandmulti-threadinghardwareisautomaticallyexploitedbythebuilt-inscheduler,whichmultiplexesmultipleOSthreadsoverthenodesreadyforexecution.

1.2 GraphicalprogrammingLabVIEWtiesthecreationofuserinterfaces(calledfrontpanels)intothedevelopmentcycle.LabVIEWprograms/subroutinesarecalledvirtualinstruments(VIs).EachVIhasthreecomponents:ablockdiagram,afrontpanel,andaconnectorpanel.ThelastisusedtorepresenttheVIintheblockdiagramsofother,callingVIs.Controlsandindicatorsonthefrontpanelallowanoperatortoinputdataintoorextractdatafromarunningvirtualinstrument.However,thefrontpanelcanalsoserveasaprogrammaticinterface.Thusavirtualinstrumentcaneitherberunasaprogram,withthefrontpanelservingasauserinterface,or,whendroppedasanodeontotheblockdiagram,thefrontpaneldefinesthe

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inputsandoutputsforthegivennodethroughtheconnectorpane.ThisimplieseachVIcanbeeasilytestedbeforebeingembeddedasasubroutineintoalargerprogram.

Thegraphicalapproachalsoallowsnon-programmerstobuildprogramssimplybydragginganddroppingvirtualrepresentationsoflabequipmentwithwhichtheyarealreadyfamiliar.TheLabVIEWprogrammingenvironment,withtheincludedexamplesandthedocumentation,makesitsimpletocreatesmallapplications.Thisisabenefitononeside,butthereisalsoacertaindangerofunderestimatingtheexpertiseneededforgoodquality"G"programming.Forcomplexalgorithmsorlarge-scalecode,itisimportantthattheprogrammerpossessanextensiveknowledgeofthespecialLabVIEWsyntaxandthetopologyofitsmemorymanagement.ThemostadvancedLabVIEWdevelopmentsystemsofferthepossibilityofbuildingstand-aloneapplications.Furthermore,itispossibletocreatedistributedapplications,whichcommunicatebyaclient/serverscheme,andarethereforeeasiertoimplementduetotheinherentlyparallelnatureofG-code.

1.3 BenefitsOnebenefitofLabVIEWoverotherdevelopmentenvironmentsistheextensivesupportforaccessinginstrumentationhardware.Driversandabstractionlayersformanydifferenttypesofinstrumentsandbusesareincludedorareavailableforinclusion.Thesepresentthemselvesasgraphicalnodes.Theabstractionlayersofferstandardsoftwareinterfacestocommunicatewithhardwaredevices.Theprovideddriverinterfacessaveprogramdevelopmenttime.ThesalespitchofNationalInstrumentsis,therefore,thatevenpeoplewithlimitedcodingexperiencecanwriteprogramsanddeploytestsolutionsinareducedtimeframewhencomparedtomoreconventionalorcompetingsystems.Anewhardwaredrivertopology(DAQmxBase),whichconsistsmainlyofG-codedcomponentswithonlyafewregistercallsthroughNIMeasurementHardwareDDK(DriverDevelopmentKit)functions,providesplatformindependenthardwareaccesstonumerousdataacquisitionandinstrumentationdevices.TheDAQmxBasedriverisavailableforLabVIEWonWindows,MacOSXandLinuxplatforms.

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2 DatabaseSystemsAdatabaseisanintegratedcollectionoflogicallyrelatedrecordsorfilesconsolidatedintoacommonpoolthatprovidesdataforoneormoremultipleuses.

Onewayofclassifyingdatabasesinvolvesthetypeofcontent,forexample:bibliographic,full-text,numeric,andimage.Otherclassificationmethodsstartfromexaminingdatabasemodelsordatabasearchitectures.

Thedatainadatabaseisorganizedaccordingtoadatabasemodel.Therelationalmodelisthemostcommon.

ADatabaseManagementSystem(DBMS)consistsofsoftwarethatorganizesthestorageofdata.ADBMScontrolsthecreation,maintenance,anduseofthedatabasestoragestructuresoforganizationsandoftheirendusers.Itallowsorganizationstoplacecontroloforganization-widedatabasedevelopmentinthehandsofDatabaseAdministrators(DBAs)andotherspecialists.Inlargesystems,aDBMSallowsusersandothersoftwaretostoreandretrievedatainastructuredway.

Databasemanagementsystemsareusuallycategorizedaccordingtothedatabasemodelthattheysupport,suchasthenetwork,relationalorobjectmodel.Themodeltendstodeterminethequerylanguagesthatareavailabletoaccessthedatabase.OnecommonlyusedquerylanguagefortherelationaldatabaseisSQL,althoughSQLsyntaxandfunctioncanvaryfromoneDBMStoanother.AgreatdealoftheinternalengineeringofaDBMSisindependentofthedatamodel,andisconcernedwithmanagingfactorssuchasperformance,concurrency,integrity,andrecoveryfromhardwarefailures.Intheseareastherearelargedifferencesbetweenproducts.

2.1 RDBMSComponentsARelationalDatabaseManagementSystem(DBMS)consistsofthefollowingcomponents:

• Interfacedrivers-Auserorapplicationprograminitiateseitherschemamodificationorcontentmodification.ThesedriversarebuiltontopofSQL.Theyprovidemethodstopreparestatements,executestatements,fetchresults,etc.AnimportantexampleistheODBCdriver.

• SQLengine-ThiscomponentinterpretsandexecutestheSQLquery.Itcomprisesthreemajorcomponents(compiler,optimizer,andexecutionengine).

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• Transactionengine-Transactionsaresequencesofoperationsthatreadorwritedatabaseelements,whicharegroupedtogether.

• Relationalengine-RelationalobjectssuchasTable,Index,andReferentialintegrityconstraintsareimplementedinthiscomponent.

• Storageengine-Thiscomponentstoresandretrievesdatarecords.Italsoprovidesamechanismtostoremetadataandcontrolinformationsuchasundologs,redologs,locktables,etc.

2.2 DatawarehouseAdatawarehousestoresdatafromcurrentandpreviousyears—dataextractedfromthevariousoperationaldatabasesofanorganization.Itbecomesthecentralsourceofdatathathasbeenscreened,edited,standardizedandintegratedsothatitcanbeusedbymanagersandotherend-userprofessionalsthroughoutanorganization.

2.3 RelationalDatabaseArelationaldatabasematchesdatausingcommoncharacteristicsfoundwithinthedataset.Theresultinggroupsofdataareorganizedandaremucheasierforpeopletounderstand.

Forexample,adatasetcontainingallthereal-estatetransactionsinatowncanbegroupedbytheyearthetransactionoccurred;oritcanbegroupedbythesalepriceofthetransaction;oritcanbegroupedbythebuyer'slastname;andsoon.

Suchagroupingusestherelationalmodel(atechnicaltermforthisisschema).Hence,suchadatabaseiscalleda"relationaldatabase."

Thesoftwareusedtodothisgroupingiscalledarelationaldatabasemanagementsystem.Theterm"relationaldatabase"oftenreferstothistypeofsoftware.

Relationaldatabasesarecurrentlythepredominantchoiceinstoringfinancialrecords,manufacturingandlogisticalinformation,personneldataandmuchmore.

Strictly,arelationaldatabaseisacollectionofrelations(frequentlycalledtables).

2.4 Real-timedatabasesAreal-timedatabaseisaprocessingsystemdesignedtohandleworkloadswhosestatemaychangeconstantly.Thisdiffersfromtraditionaldatabasescontainingpersistentdata,mostlyunaffectedbytime.Forexample,astockmarketchangesrapidlyanddynamically.Real-time

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processingmeansthatatransactionisprocessedfastenoughfortheresulttocomebackandbeactedonrightaway.Real-timedatabasesareusefulforaccounting,banking,law,medicalrecords,multi-media,processcontrol,reservationsystems,andscientificdataanalysis.Ascomputersincreaseinpowerandcanstoremoredata,real-timedatabasesbecomeintegratedintosocietyandareemployedinmanyapplications

2.5 DatabaseManagementSystemsThereareDatabaseManagementSystems(DBMS),suchas:

• MicrosoftSQLServer• Oracle• Sybase• dBase• MicrosoftAccess• MySQLfromSunMicrosystems(Oracle)• DB2fromIBM• etc.

ThisdocumentwillfocusonMicrosoftAccessandMicrosoftSQLServer.

2.6 MDACTheMicrosoftDataAccessComponents(MDAC)istheframeworkthatmakesitpossibletoconnectandcommunicatewiththedatabase.MDACincludesthefollowingcomponents:

• ODBC(OpenDatabaseConnectivity)• OLEDB• ADO(ActiveXDataObjects)

MDACalsoinstallsseveraldataprovidersyoucanusetoopenaconnectiontoaspecificdatasource,suchasanMSAccessdatabase.

2.6.1 ODBC

OpenDatabaseConnectivity(ODBC)isanativeinterfacethatisaccessedthroughaprogramminglanguagethatcanmakecallsintoanativelibrary.InMDACthisinterfaceisdefinedasaDLL.Aseparatemoduleordriverisneededforeachdatabasethatmustbeaccessed.

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2.6.2 OLEDB

OLEallowsMDACapplicationsaccesstodifferenttypesofdatastoresinauniformmanner.Microsofthasusedthistechnologytoseparatetheapplicationfromthedatastorethatitneedstoaccess.Thiswasdonebecausedifferentapplicationsneedaccesstodifferenttypesandsourcesofdata,anddonotnecessarilyneedtoknowhowtoaccesstechnology-specificfunctionality.Thetechnologyisconceptuallydividedintoconsumersandproviders.Theconsumersaretheapplicationsthatneedaccesstothedata,andtheprovideristhesoftwarecomponentthatexposesanOLEDBinterfacethroughtheuseoftheComponentObjectModel(orCOM).

2.6.3 ADO(ActiveXDataObjects)

ActiveXDataObjects(ADO)isahighlevelprogramminginterfacetoOLEDB.Itusesahierarchicalobjectmodeltoallowapplicationstoprogrammaticallycreate,retrieve,updateanddeletedatafromsourcessupportedbyOLEDB.ADOconsistsofaseriesofhierarchicalCOM-basedobjectsandcollections,anobjectthatactsasacontainerofmanyotherobjects.AprogrammercandirectlyaccessADOobjectstomanipulatedata,orcansendanSQLquerytothedatabaseviaseveralADOmechanisms.

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3 RelationalDatabasesArelationaldatabasematchesdatausingcommoncharacteristicsfoundwithinthedataset.Theresultinggroupsofdataareorganizedandaremucheasierforpeopletounderstand.

Forexample,adatasetcontainingallthereal-estatetransactionsinatowncanbegroupedbytheyearthetransactionoccurred;oritcanbegroupedbythesalepriceofthetransaction;oritcanbegroupedbythebuyer'slastname;andsoon.

Suchagroupingusestherelationalmodel(atechnicaltermforthisisschema).Hence,suchadatabaseiscalleda"relationaldatabase."

Thesoftwareusedtodothisgroupingiscalledarelationaldatabasemanagementsystem.Theterm"relationaldatabase"oftenreferstothistypeofsoftware.

Relationaldatabasesarecurrentlythepredominantchoiceinstoringfinancialrecords,manufacturingandlogisticalinformation,personneldataandmuchmore.

3.1 TablesThebasicunitsinadatabasearetablesandtherelationshipbetweenthem.Strictly,arelationaldatabaseisacollectionofrelations(frequentlycalledtables).

3.2 UniqueKeysandPrimaryKey

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Inrelationaldatabasedesign,auniquekeyorprimarykeyisacandidatekeytouniquelyidentifyeachrowinatable.Auniquekeyorprimarykeycomprisesasinglecolumnorsetofcolumns.Notwodistinctrowsinatablecanhavethesamevalue(orcombinationofvalues)inthosecolumns.Dependingonitsdesign,atablemayhavearbitrarilymanyuniquekeysbutatmostoneprimarykey.

Auniquekeymustuniquelyidentifyallpossiblerowsthatexistinatableandnotonlythecurrentlyexistingrows.ExamplesofuniquekeysareSocialSecuritynumbersorISBNs.

Aprimarykeyisaspecialcaseofuniquekeys.ThemajordifferenceisthatforuniquekeystheimplicitNOTNULLconstraintisnotautomaticallyenforced,whileforprimarykeysitisenforced.Thus,thevaluesinuniquekeycolumnsmayormaynotbeNULL.Anotherdifferenceisthatprimarykeysmustbedefinedusinganothersyntax.

Primarykeysaredefinedwiththefollowingsyntax:

CREATE TABLE table_name ( id_col INT, col2 CHARACTER VARYING(20), ... CONSTRAINT tab_pk PRIMARY KEY(id_col), ... )

Iftheprimarykeyconsistsonlyofasinglecolumn,thecolumncanbemarkedassuchusingthefollowingsyntax:

CREATE TABLE table_name ( id_col INT PRIMARY KEY, col2 CHARACTER VARYING(20), ... )

Thedefinitionofuniquekeysissyntacticallyverysimilartoprimarykeys.

Likewise,uniquekeyscanbedefinedaspartoftheCREATETABLESQLstatement.

CREATE TABLE table_name ( id_col INT, col2 CHARACTER VARYING(20), key_col SMALLINT, ... CONSTRAINT key_unique UNIQUE(key_col), ... )

Oriftheuniquekeyconsistsonlyofasinglecolumn,thecolumncanbemarkedassuchusingthefollowingsyntax:

CREATE TABLE table_name (



id_col INT PRIMARY KEY, col2 CHARACTER VARYING(20), ... key_col SMALLINT UNIQUE, ... )

3.3 ForeignKeyInthecontextofrelationaldatabases,aforeignkeyisareferentialconstraintbetweentwotables.Theforeignkeyidentifiesacolumnorasetofcolumnsinonetablethatreferstoacolumnorsetofcolumnsinanothertable.Thecolumnsinthereferencingtablemustbetheprimarykeyorothercandidatekeyinthereferencedtable.Thevaluesinonerowofthereferencingcolumnsmustoccurinasinglerowinthereferencedtable.Thus,arowinthereferencingtablecannotcontainvaluesthatdon'texistinthereferencedtable.Thiswayreferencescanbemadetolinkinformationtogetheranditisanessentialpartofdatabasenormalization.Multiplerowsinthereferencingtablemayrefertothesamerowinthereferencedtable.Mostofthetime,itreflectstheone(mastertable,orreferencedtable)tomany(childtable,orreferencingtable)relationship.

Thereferencingandreferencedtablemaybethesametable,i.e.theforeignkeyrefersbacktothesametable.Suchaforeignkeyisknownasself-referencingorrecursiveforeignkey.

Atablemayhavemultipleforeignkeys,andeachforeignkeycanhaveadifferentreferencedtable.Eachforeignkeyisenforcedindependentlybythedatabasesystem.Therefore,cascadingrelationshipsbetweentablescanbeestablishedusingforeignkeys.

Improperforeignkey/primarykeyrelationshipsornotenforcingthoserelationshipsareoftenthesourceofmanydatabaseanddatamodelingproblems.

ForeignkeyscanbedefinedaspartoftheCREATETABLESQLstatement.

CREATE TABLE table_name ( id INTEGER PRIMARY KEY, col2 CHARACTER VARYING(20), col3 INTEGER, ... CONSTRAINT col3_fk FOREIGN KEY(col3) REFERENCES other_table(key_col), ... )

Iftheforeignkeyisasinglecolumnonly,thecolumncanbemarkedassuchusingthefollowingsyntax:

CREATE TABLE table_name ( id INTEGER PRIMARY KEY, col2 CHARACTER VARYING(20),



col3 INTEGER REFERENCES other_table(column_name), ... )

3.4 ViewsIndatabasetheory,aviewconsistsofastoredqueryaccessibleasavirtualtablecomposedoftheresultsetofaquery.Unlikeordinarytablesinarelationaldatabase,aviewdoesnotformpartofthephysicalschema:itisadynamic,virtualtablecomputedorcollatedfromdatainthedatabase.Changingthedatainatablealtersthedatashowninsubsequentinvocationsoftheview.

Viewscanprovideadvantagesovertables:

• Viewscanrepresentasubsetofthedatacontainedinatable • Viewscanjoinandsimplifymultipletablesintoasinglevirtualtable • Viewscanactasaggregatedtables,wherethedatabaseengineaggregatesdata

(sum,averageetc)andpresentsthecalculatedresultsaspartofthedata • Viewscanhidethecomplexityofdata;forexampleaviewcouldappearasSales2000

orSales2001,transparentlypartitioningtheactualunderlyingtable • Viewstakeverylittlespacetostore;thedatabasecontainsonlythedefinitionofa

view,notacopyofallthedataitpresents • Viewscanlimitthedegreeofexposureofatableortablestotheouterworld

Syntax:

CREATE VIEW <ViewName> AS …

3.5 FunctionsInSQLdatabases,auser-definedfunctionprovidesamechanismforextendingthefunctionalityofthedatabaseserverbyaddingafunctionthatcanbeevaluatedinSQLstatements.TheSQLstandarddistinguishesbetweenscalarandtablefunctions.Ascalarfunctionreturnsonlyasinglevalue(orNULL),whereasatablefunctionreturnsa(relational)tablecomprisingzeroormorerows,eachrowwithoneormorecolumns.

User-definedfunctionsinSQLaredeclaredusingtheCREATEFUNCTIONstatement.

Syntax:

CREATE FUNCTION <FunctionName> (@Parameter1 <datatype>, @ Parameter2 <datatype>,



…) RETURNS <datatype> AS …

3.6 StoredproceduresAstoredprocedureisexecutablecodethatisassociatedwith,andgenerallystoredin,thedatabase.Storedproceduresusuallycollectandcustomizecommonoperations,likeinsertingatupleintoarelation,gatheringstatisticalinformationaboutusagepatterns,orencapsulatingcomplexbusinesslogicandcalculations.Frequentlytheyareusedasanapplicationprogramminginterface(API)forsecurityorsimplicity.

Storedproceduresarenotpartoftherelationaldatabasemodel,butallcommercialimplementationsincludethem.

Storedproceduresarecalledorusedwiththefollowingsyntax:

CALL procedure(…)

or

EXECUTE procedure(…)

Storedprocedurescanreturnresultsets,i.e.theresultsofaSELECTstatement.Suchresultsetscanbeprocessedusingcursorsbyotherstoredproceduresbyassociatingaresultsetlocator,orbyapplications.Storedproceduresmayalsocontaindeclaredvariablesforprocessingdataandcursorsthatallowittoloopthroughmultiplerowsinatable.ThestandardStructuredQueryLanguageprovidesIF,WHILE,LOOP,REPEAT,CASEstatements,andmore.Storedprocedurescanreceivevariables,returnresultsormodifyvariablesandreturnthem,dependingonhowandwherethevariableisdeclared.

3.7 TriggersAdatabasetriggerisproceduralcodethatisautomaticallyexecutedinresponsetocertaineventsonaparticulartableorviewinadatabase.Thetriggerismostlyusedforkeepingtheintegrityoftheinformationonthedatabase.Forexample,whenanewrecord(representinganewworker)addedtotheemployeestable,newrecordsshouldbecreatedalsointhetablesofthetaxes,vacations,andsalaries.

Thesyntaxisasfollows:

CREATE TRIGGER <TriggerName> ON <TableName>



FOR INSERT, UPDATE, DELETE AS …

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4 StructuredQueryLanguage(SQL)

SQL(StructuredQueryLanguage)isadatabasecomputerlanguagedesignedformanagingdatainrelationaldatabasemanagementsystems(RDBMS).

4.1 QueriesThemostcommonoperationinSQListhequery,whichisperformedwiththedeclarativeSELECTstatement.SELECTretrievesdatafromoneormoretables,orexpressions.StandardSELECTstatementshavenopersistenteffectsonthedatabase.

Queriesallowtheusertodescribedesireddata,leavingthedatabasemanagementsystem(DBMS)responsibleforplanning,optimizing,andperformingthephysicaloperationsnecessarytoproducethatresultasitchooses.

AqueryincludesalistofcolumnstobeincludedinthefinalresultimmediatelyfollowingtheSELECTkeyword.Anasterisk("*")canalsobeusedtospecifythatthequeryshouldreturnallcolumnsofthequeriedtables.SELECTisthemostcomplexstatementinSQL,withoptionalkeywordsandclausesthatinclude:

• TheFROMclausewhichindicatesthetable(s)fromwhichdataistoberetrieved.TheFROMclausecanincludeoptionalJOINsubclausestospecifytherulesforjoiningtables.

• TheWHEREclauseincludesacomparisonpredicate,whichrestrictstherowsreturnedbythequery.TheWHEREclauseeliminatesallrowsfromtheresultsetforwhichthecomparisonpredicatedoesnotevaluatetoTrue.

• TheGROUPBYclauseisusedtoprojectrowshavingcommonvaluesintoasmallersetofrows.GROUPBYisoftenusedinconjunctionwithSQLaggregationfunctionsortoeliminateduplicaterowsfromaresultset.TheWHEREclauseisappliedbeforetheGROUPBYclause.

• TheHAVINGclauseincludesapredicateusedtofilterrowsresultingfromtheGROUPBYclause.BecauseitactsontheresultsoftheGROUPBYclause,aggregationfunctionscanbeusedintheHAVINGclausepredicate.



• TheORDERBYclauseidentifieswhichcolumnsareusedtosorttheresultingdata,andinwhichdirectiontheyshouldbesorted(optionsareascendingordescending).WithoutanORDERBYclause,theorderofrowsreturnedbyanSQLqueryisundefined.

Example:

ThefollowingisanexampleofaSELECTquerythatreturnsalistofexpensivebooks.ThequeryretrievesallrowsfromtheBooktableinwhichthepricecolumncontainsavaluegreaterthan100.00.Theresultissortedinascendingorderbytitle.Theasterisk(*)intheselectlistindicatesthatallcolumnsoftheBooktableshouldbeincludedintheresultset.

SELECT * FROM Book WHERE price > 100.00 ORDER BY title;

Theexamplebelowdemonstratesaqueryofmultipletables,grouping,andaggregation,byreturningalistofbooksandthenumberofauthorsassociatedwitheachbook.

SELECT Book.title,count(*) AS Authors FROM Book JOIN Book_author ON Book.isbn = Book_author.isbn GROUP BY Book.title

Exampleoutputmightresemblethefollowing:

Title Authors ------------------------------- SQL Examples and Guide 4 The Joy of SQL 1 An Introduction to SQL 2 Pitfalls of SQL 1

4.2 DatamanipulationTheDataManipulationLanguage(DML)isthesubsetofSQLusedtoadd,updateanddeletedata.

TheacronymCRUDreferstoallofthemajorfunctionsthatneedtobeimplementedinarelationaldatabaseapplicationtoconsideritcomplete.EachletterintheacronymcanbemappedtoastandardSQLstatement:

Operation SQL

Create INSERT

Read(Retrieve) SELECT



Update UPDATE

Delete(Destroy) DELETE

Example:INSERT

INSERTaddsrowstoanexistingtable,e.g.,:

INSERT INTO My_table field1, field2, field3) VALUES ('test', 'N', NULL)

Example:UPDATE

UPDATEmodifiesasetofexistingtablerows,e.g.,:

UPDATE My_table SET field1 = 'updated value' WHERE field2 = 'N'

Example:DELETE

DELETEremovesexistingrowsfromatable,e.g.,:

DELETE FROM My_table WHERE field2 = 'N'

4.3 DatadefinitionTheDataDefinitionLanguage(DDL)managestableandindexstructure.ThemostbasicitemsofDDLaretheCREATE,ALTER,RENAMEandDROPstatements:

• CREATEcreatesanobject(atable,forexample)inthedatabase. • DROPdeletesanobjectinthedatabase,usuallyirretrievably. • ALTERmodifiesthestructureanexistingobjectinvariousways—forexample,adding

acolumntoanexistingtable.

Example:CREATE

CreateaDatabaseTable

CREATE TABLE My_table ( my_field1 INT, my_field2 VARCHAR(50), my_field3 DATE NOT NULL, PRIMARY KEY (my_field1) )



4.4 DatatypesEachcolumninanSQLtabledeclaresthetype(s)thatcolumnmaycontain.ANSISQLincludesthefollowingdatatypes.

4.4.1 Characterstrings

• CHARACTER(n)orCHAR(n)—fixed-widthn-characterstring,paddedwithspacesasneeded

• CHARACTERVARYING(n)orVARCHAR(n)—variable-widthstringwithamaximumsizeofncharacters

• NATIONALCHARACTER(n)orNCHAR(n)—fixedwidthstringsupportinganinternationalcharacterset

• NATIONALCHARACTERVARYING(n)orNVARCHAR(n)—variable-widthNCHARstring

4.4.2 Bitstrings

• BIT(n)—anarrayofnbits • BITVARYING(n)—anarrayofuptonbits

4.4.3 Numbers

• INTEGERandSMALLINT • FLOAT,REALandDOUBLEPRECISION • NUMERIC(precision,scale)orDECIMAL(precision,scale)

4.4.4 DateandTime

• DATE • TIME • TIMESTAMP • INTERVAL

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5 DatabaseModelling

5.1 ERDiagramInsoftwareengineering,anEntity-RelationshipModel(ERM)isanabstractandconceptualrepresentationofdata.Entity-relationshipmodelingisadatabasemodelingmethod,usedtoproduceatypeofconceptualschemaorsemanticdatamodelofasystem,oftenarelationaldatabase,anditsrequirementsinatop-downfashion.

Diagramscreatedusingthisprocessarecalledentity-relationshipdiagrams,orERdiagramsorERDsforshort.

[Wikipedia]

TherearemanyERdiagrammingtools.SomeoftheproprietaryERdiagrammingtoolsareERwin,EnterpriseArchitectandMicrosoftVisio.

MicrosoftSQLServerhasalsoabuilt-intoolforcreatingDatabaseDiagrams.

18 DatabaseModelling


5.2 MicrosoftVisioMicrosoftVisioisadiagrammingprogramforcreatingdifferentkindsofdiagrams.VisiohaveatemplateforcreatingDatabaseModelDiagrams.

IntheDatabasemenuVisioofferslotsoffunctionalityregardingyourdatabasemodel.



“ReverseEngineering”istheoppositeprocedure,i.e.,extractionofadatabaseschemafromanexistingdatabaseintoadatabasemodelinMicrosoftVisio.

5.3 ExercisesExercise:DatabaseDiagram

CreatethefollowingtablesinanERDiagramusingMSVisio.

• CUSTOMERo CustomerId(PK)o FirstNameo LastNameo Addresso Phoneo PostCodeo PostAddress

• PRODUCTo ProductId(PK)o ProductNameo ProductDescriptiono Priceo ProductCode

• ORDERo OrderId(PK)o OrderNumber



o OrderDescriptiono CustomerId(FK)

• ORDER_DETAILo OrderDetailId(PK)o OrderId(FK)o ProductId(FK)

DatabaseDiagram:

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6 MicrosoftSQLServer

6.1 IntroductionMicrosoftSQLServerisarelationalmodeldatabaseserverproducedbyMicrosoft.ItsprimaryquerylanguagesareT-SQLandANSISQL.

ThelatestversionisMicrosoftSQLServer2008.

MicrosoftSQLServerhomepage:www.microsoft.com/sqlserver

TheMicrosoftSQLServercomesindifferentversions,suchas:

• SQLServerDeveloperEdition• SQLServerEnterpriseEdition• SQLServerWebEdition• SQLServerExpressEdition• Etc.

TheSQLServerExpressEditionisafreely-downloadableand-distributableversion.

6.2 RequirementsInordertoinstallSQLServer2008,youneed:

• Microsoft.NETFramework3.5SP1• WindowsInstaller4.5• WindowsPowerShell1.0

Note:YoumusthaveadministrativerightsonthecomputertoinstallMicrosoftSQLServer2008.

6.3 SQLServerExpressTheSQLServerExpressEditionisafreely-downloadableand-distributableversion.



However,theExpresseditionhasanumberoftechnicalrestrictionswhichmakeitundesirableforlarge-scaledeployments,including:

• Maximumdatabasesizeof4GBper.The4GBlimitappliesperdatabase(logfilesexcluded);butinsomescenariosuserscanaccessmoredatathroughtheuseofmultipleinterconnecteddatabases.

• SinglephysicalCPU,multiplecores • 1GBofRAM(runsonanysizeRAMsystem,butusesonly1GB)

SQLServerExpressoffersaGUItoolsfordatabasemanagementinaseparatedownloadandinstallationpackage,calledSQLServerManagementStudioExpress.

6.4 AdventureWorksTheAdventureWorksisasampleDatabasewithlotsofexamples,etc.

YoushouldinstallthissampleDatabasebecausesomeoftheexamplesinthisdocumentwillusetheAdventureWorksdatabase.

6.5 SQLServerManagementStudioSQLServerManagementStudioisaGUItoolincludedwithSQLServerforconfiguring,managing,andadministeringallcomponentswithinMicrosoftSQLServer.Thetoolincludesbothscripteditorsandgraphicaltoolsthatworkwithobjectsandfeaturesoftheserver.Asmentionedearlier,versionofSQLServerManagementStudioisalsoavailableforSQLServerExpressEdition,forwhichitisknownasSQLServerManagementStudioExpress.

AcentralfeatureofSQLServerManagementStudioistheObjectExplorer,whichallowstheusertobrowse,select,andactuponanyoftheobjectswithintheserver.Itcanbeusedtovisuallyobserveandanalyzequeryplansandoptimizethedatabaseperformance,amongothers.SQLServerManagementStudiocanalsobeusedtocreateanewdatabase,alteranyexistingdatabaseschemabyaddingormodifyingtablesandindexes,oranalyzeperformance.ItincludesthequerywindowswhichprovideaGUIbasedinterfacetowriteandexecutequeries.



6.6 CreateanewDatabaseItisquitesimpletocreateanewdatabaseinMicrosoftSQLServer.Justright-clickonthe“Databases”nodeandselect“NewDatabase…”



Therearelotsofsettingsyoumaysetregardingyourdatabase,buttheonlyinformationyoumustfillinisthenameofyourdatabase:

6.7 Backup/RestoreAnimportanttaskindatabasesystemsistotakebackupofthedatabasewithregularintervals,e.g.,duringthenightwhenthesystemisnotinuse.

DatabasebackupandRestore:



6.8 ExampleDatabaseExamplesandexercisesinthistrainingarebasedonsomebasictables.TheExampleDatabaseconsistsofthefollowingTables:




• PRODUCTo ProductId(PK)o ProductNameo ProductDescriptiono Priceo ProductCode

• ORDERo OrderId(PK)o OrderNumbero OrderDescriptiono CustomerId(FK)




6.9 ExercisesExercise:NewDatabase

CreateanewDatabaseinMSSQLServercalledTEST_SQLSERVER.

Exercise:DatabaseDiagram

CreatethetablesintheExampleDatabaseusingtheDiagramDesignerToolinMicrosoftSQLServer.

Exercise:DatabaseScript

CreatethetablesintheExampleDatabaseTablesusingSQLCode.SavetheTablesasaSQLScriptfile(.sql).UseTheQueryToolinMicrosoftSQLServer.

Exercise:ODBC

CreateanODBCconnectionfortheDatabase.

28

7 MicrosoftOfficeAccess

7.1 IntroductionMicrosoftOfficeAccess,previouslyknownasMicrosoftAccess,isarelationaldatabasemanagementsystemfromMicrosoftthatcombinestherelationalMicrosoftJetDatabaseEnginewithagraphicaluserinterfaceandsoftwaredevelopmenttools.ItisamemberoftheMicrosoftOfficesuiteofapplicationsandisincludedintheProfessionalandhigherversionsforWindows.AccessstoresdatainitsownformatbasedontheAccessJetDatabaseEngine.

MicrosoftAccessisusedbyprogrammersandnon-programmerstocreatetheirownsimpledatabasesolutions.

MicrosoftAccessisafileserver-baseddatabase.Unlikeclient-serverrelationaldatabasemanagementsystems(RDBMS),e.g.,MicrosoftSQLServer,MicrosoftAccessdoesnotimplementdatabasetriggers,storedprocedures,ortransactionlogging.Alldatabasetables,queries,forms,reports,macros,andmodulesarestoredintheAccessJetdatabaseasasinglefile.ThismakesMicrosoftAccessusefulinsmallapplications,teaching,etc.becauseitiseasytomovefromonecomputertoanother.

7.2 ExampleDatabaseIwillpresentanexampledatabaseinMicrosoftAccess2007whichwillbeusedinsomeoftheexamplesandexercisesinthisdocument.

Thedatabaseconsistsofthefollowingtables:


• PRODUCT



o ProductId(PK)o ProductNameo ProductDescriptiono Priceo ProductCode

• ORDERo OrderId(PK)o OrderNumbero OrderDescriptiono CustomerId(FK)


ODBCConnection:

AdministrativeTools→DataSources(ODBC)



7.3 ExercisesExercise:Database

CreateanewDatabaseinMSAccesscalledTEST.

Exercise:DatabaseTables



CreatethetablesintheExampleDatabaseTablesusingtheDiagramDesignerToolinMicrosoftSQLServer.

Exercise:ODBC

CreateanODBCconnectionfortheDatabase.

32

8 ODBC8.1 WhatisODBC?Incomputing,OpenDatabaseConnectivity(ODBC)providesastandardsoftwareAPImethodforusingdatabasemanagementsystems(DBMS).ThedesignersofODBCaimedtomakeitindependentofprogramminglanguages,databasesystems,andoperatingsystems.

8.2 CreateanODBCConnectionin“ODBCDataSourceAdministrator”

Followthesesteps:

AddanewDataSourceandselecttheSQLServerdriver:

TypeaNameforyourConnectionandyourSQLServerName.YoufindyourServernameasshownbelow:

33 ODBC


SelectSQLServerauthenticationandtypeyoursapassword(SystemAdministrator). YoudefinedthepasswordforthesauserduringthesetupprocedureofSQLServer:

CompleteyourconfigurationandTestyourdatasourcetoseeifitsOK:

34 ODBC


Ifyougetthismessageyouhavesucceeded:

8.3 GetdataintoExcelusingyourODBCConnection

ThepurposeistouseExcelasaclientandgetdataintoExcelfromyourSQLServer.

Step1:OpenExcelandgototheDatasection:

35 ODBC


Step2:SelectyourODBCconnection

Step3:SelectyourTable(s)

36 ODBC


Step4:InsertDataintoExcel

Theresultsshouldlooksomethinglikethis:

37 ODBC


38

9 LabVIEWDatabaseConnectivityToolkit

LabVIEWoffersanadditionalToolkitcalled“LabVIEWDatabaseConnectivityToolkit”.Withthistoolkityoucancommunicatewithdifferentdatabases,suchasSQLServer,Oracle,etc.

FunctionsPalette:Connectivity→Database

ThefollowinglistdescribesthemainfeaturesoftheDatabaseConnectivityToolkit:

• WorkswithanyproviderthatadherestotheMicrosoftActiveXDataObject(ADO)standard.

• WorkswithanydatabasedriverthatcomplieswithODBCorOLEDB.• Maintainsahighlevelofportability.Inmanycases,youcanportanapplicationto

anotherdatabasebychangingtheconnectioninformationyoupasstotheDBToolsOpenConnectionVI.

• ConvertsdatabasecolumnvaluesfromnativedatatypestostandardDatabaseConnectivityToolkitdatatypes,furtherenhancingportability.

• PermitstheuseofSQLstatementswithallsupporteddatabasesystems,evennon-SQLsystems.

• IncludesVIstoretrievethenameanddatatypeofacolumnreturnedbyaSELECTstatement.

• Createstablesandselects,inserts,updates,anddeletesrecordswithoutusingSQLstatements.



Someofthetextinthischapterisbasedonthe“LabVIEWDatabaseConnectivityToolkitUserManual”.

9.1 ConnecttotheDatabaseBeforeyoucanaccessdatainatableorexecuteSQLstatements,youmustestablishaconnectiontoadatabase.Youmayusedifferentmethodsinordertoconnecttothedatabase:

• ODBCDataSourceName(DSN)• UniversalDataLink(UDL)• ConnectionString

Thesedifferentmethodsareexplainedbelow.

Forallofthesemethods,youwillusethesameVI:

Connectingtoadatabaseiswheremosterrorsoccurbecauseeachdatabasemanagementsystem(DBMS)usesdifferentparametersfortheconnectionanddifferentlevelsofsecurity.Thedifferentstandardsalsousedifferentmethodsofconnectingtodatabases.Forexample,ODBCusesDataSourceNames(DSN)fortheconnection,whereastheMicrosoftActiveXDataObject(ADO)standardusesUniversalDataLinks(UDL)fortheconnection.The“DBToolsOpenConnection.vi”VIsupportsallthesemethodsforconnectingtoadatabase.

Whenyouarefinishedwithreadingfromthedatabaseandwritingtothedatabase,youshouldalwaysclosetheConnection.Usethe“DBToolsCloseConnection.vi”.



9.1.1 DSN

ADSN(ODBCDataSourceName(DSN))isthenameofthedatasource,ordatabase,towhichyouareconnecting.TheDSNalsocontainsinformationabouttheODBCdriverandotherconnectionattributesincludingpaths,securityinformation,andread-onlystatusofthedatabase.TwomaintypesofDSNsexist:machineDSNsandfileDSNs.MachineDSNsareinthesystemregistryandapplytoallusersofthecomputersystemortoasingleuser.DSNsthatapplytoallusersofacomputersystemaresystemDSNs.DSNsthatapplytosingleusersareuserDSNs.AfileDSNisatextfilewitha.dsnextensionandisaccessibletoanyonewithproperpermissions.FileDSNsarenotrestrictedtoasingleuserorcomputersystem.UsetheODBCDataSourceAdministratortocreateandconfigureDSNs.

IntheControlPanel,AdministrativeTools,youfindtheODBCDataSourceAdministratortool.



Example:DSN

ThisExamplespecifiesaDSNcalledMSAccesstoopenaconnectiontothatspecificdatabase.

Example:DSNfromFile

YoucanuseapathtospecifyafileDSN.ThisexamplespecifiesapathtoafileDSNcalled“access.dsn”toopenaconnectiontothedatabase.

Example:DSNwithUserIdandPassword

MostDatabasesystems(DBMS–DatabaseManagementSystems)alsorequireaUserIdandaPassword.

9.1.2 UDL

WhereasyoumustcreateaDSNtoconnecttoadatabaseusingODBC,youuseUDL(UniversalDataLink)toconnecttodatabasesthatuseADOandOLEDB.

AUDLissimilartoaDSNinthatitdescribesmorethanjustthedatasource.AUDLspecifieswhatOLEDBproviderisused,serverinformation,theuserIDandpassword,thedefaultdatabase,andotherrelatedinformation.

InordertocreateanewUDLfile,createanemptytextfileandchangethefileextensionofthisdocumentfrom.txtto.udl.Youthencandouble-clicktheUDLfiletodisplaytheDataLinkPropertiesdialogbox.



Example:UDL

ConnecttoaDatabaseusingUDL:

9.1.3 ConnectionString

RatherthanincludinganexistingUDLinanapplication,youalsocanuseanODBCconnectionstringwiththeMicrosoftActiveXDataObject(ADO)standard.

Aconnectionstringiswrittenlikethis:

PROVIDER=SQLOLEDB;DATA SOURCE=server_name;UID=user_name;PWD=password;DATABASE=database_name;

Youcouldusemoreparameters,buttheparametersusedabovearethemostcommonones.

9.2 ReadingDatafromtheDatabase



Readingdatafromadatabasetableissimilartowritingdatatothedatabase.Youopenaconnectiontothedatabase,selectthedatafromatable,andthenclosetheconnection.

The“DBToolsSelectData.vi"isusedtoreaddatafromtheDatabase:

Example:SelectDatafromMSAccess

ThefollowingexamplegetsdatafromtheCUSTOMERtableinMSAccess.

TheFrontPanellookslikethis:

NoticeinFigures5-4and5-5thatthedatabasedataisreturnedasatwo-dimensionalarrayofvariants.Asthenameimplies,theMicrosoftActiveXDataObject(ADO)standardisbased



onActiveX,whichdefinesvariantsasitsdatatypes.VariantsworkwellinlanguagessuchasVisualBasicthatarenotstronglytyped.BecauseLabVIEWisstronglytyped,youmustusetheDatabaseVariantToDatafunctiontoconvertthevariantdatatoaLabVIEWdatatypebeforeyoucandisplaythedatainstandardindicatorssuchasgraphs,charts,andLEDs.

Example:SelectDatafromMSAccess

ThefollowingexamplegetsdatafromtheCUSTOMERtableinMSAccessandconvertsthedatatotext.

TheFrontPanellookslikethis:

Youmayreadfrommorethanonetableifyouuseacomma-delimitedstringtospecifymultipletablenames:



Youmayselectwhichcolumnsyouwanttoreadbyusingthe“Columns”input:

Youmayalsorestrictwhichdatatoreceiveusingthe“optionalClause”input:

Example:ReadData

UsingsomeVIsfromthe“Advanced”palette,createthefollowingexample:



9.3 WritingDatatotheDatabaseWritingdatatoadatabasewiththeLabVIEWDatabaseConnectivityToolkitissimilartoreadingdatatoafile.Youopenaconnection,insertthedata,andclosetheconnectionwhenyouarefinished.

The“DBToolsInsertData.vi"isusedtowritedatatotheDatabase:

Example:WriteData

Createthefollowingblockdiagram:



FrontPanel:

Example:WriteData

CreatethefollowingblockdiagramusingsomeVIsfromthe“Advanced”palette.



9.4 CreatingandDroppingTablesYoumayusestandardSQLsyntaxinordertocreate:

CREATE TABLE <TableName> (…)

Oryoumayusethe“DBToolsCreateTable.vi”inordertocreateatable.

YoumayusestandardSQLsyntaxinordertodroptables(deletetables):

DROP TABLE <TableName>

Oryoumayusethe“DBToolsDropTable.vi”inordertodrop/deleteatable.



9.5 UsingtheDatabaseConnectivityToolkitUtilityVIs

Inthe“Utility”palettethereareseveralusefulVIsforgettingmoreinformationabouttables,savingtotextfiles,etc.

HereisashortdescriptionoftheVIslocatedinthe“Utility”palette:

ThisVIliststhetablesinthedatabaseidentifiedbyconnectionreference.

ThisVIliststhecolumnspresentintable.Thecolumninformationincludesthename,thedatatype,andthedefinedsizeofthecolumn.

ThisVIsetspropertiesontheobjectasdeterminedbytheinputs.

ThisVIgetspropertiesoftheobjectasdeterminedbytheinputs.

ThisVIReturnsastringcontainingtheformatteddateandtime,andidentifiesthestringasadate/timestringsootherVIscaninterpretit.

ThisVIbegins,commits,orrollsbackatransactionforanytypeofreference.



ThisVIsavestherecordsetidentifiedbytherecordsetreferencetoeitheranXMLorADTGfile.TheADTGfileformatisaproprietaryformatthatonlytheLabVIEWDatabaseConnectivityToolkitcaninterpret.TheADTGformatresultsinasmallerfilethantheXMLformat.

ThisVIloadsarecordsetfromafileandreturnsarecordsetreferencethatidentifiesthisrecordset.Youcanretrievedatafromthisrecordsetlikeanyotherrecordset,butsomepropertiesmightnotbeavailableonthisrecordset.

9.6 PerformingAdvancedDatabaseOperationsWhencreatingrealprogramsyouwillsoonneedsomeoftheVIsinthe“Advanced”palette.

HereisashortdescriptionofsomeoftheVIslocatedinthe“Advanced”palette:

ThisVIExecutesanSQLqueryandreturnsarecordsetreferencethatyoumusteventuallyfreewiththeDBToolsFreeObjectVI.

ThisVIretrievesthedataintherecordsetidentifiedbytherecordsetreferenceinput.YoucanconverteachelementinthearraytoitsnativeLabVIEWdatatypeusingthe“DatabaseVariantToDatafunction”.



ThisVIfreesanobjectbydestroyingitsassociatedreferenceandreturnsadifferentreferenceobject.

52

10 CreatingandUsingTables

TheSQLsyntaxforcreatingaTableisasfollows:

CREATE TABLE <TableName> ( <ColumnName> <datatype> … )

TheSQLsyntaxforinsertingDataintoaTableisasfollows:

INSERT INTO <TableName> (<Column1>, <Column2>, …) VALUES(<Data for Column1>, <Data for Column2>, …)

Example:InsertDataintoTables

Wewillinsertsomedataintoourtables:



ThefollowingSQLQueryinsertssomeexampledataintothesetables:

--CUSTOMER INSERT INTO [CUSTOMER] ([FirstName],[LastName],[Address],[Phone],[PostCode],[PostAddress]) VALUES ('Per', 'Nilsen', 'Vipeveien 12', '12345678', '1234', 'Porsgrunn') GO INSERT INTO [CUSTOMER] ([FirstName],[LastName],[Address],[Phone],[PostCode],[PostAddress]) VALUES ('Tor', 'Hansen', 'Vipeveien 15', '77775678', '4455', 'Bergen') GO INSERT INTO [CUSTOMER] ([FirstName],[LastName],[Address],[Phone],[PostCode],[PostAddress]) VALUES ('Arne', 'Nilsen', 'Vipeveien 17', '12345778', '4434', 'Porsgrunn') GO --PRODUCT INSERT INTO [PRODUCT] ([ProductName],[ProductDescription],[Price],[ProductCode]) VALUES ('Product A', 'This is product A', 1000, 'A-1234') GO INSERT INTO [PRODUCT] ([ProductName],[ProductDescription],[Price],[ProductCode]) VALUES ('Product B', 'This is product B', 1000, 'B-1234') GO INSERT INTO [PRODUCT] ([ProductName],[ProductDescription],[Price],[ProductCode]) VALUES ('Product C', 'This is product C', 1000, 'C-1234') GO --ORDER INSERT INTO [ORDER] ([OrderNumber],[OrderDescription],[CustomerId]) VALUES ('10001', 'This is Order 10001', 1) GO INSERT INTO [ORDER] ([OrderNumber],[OrderDescription],[CustomerId]) VALUES ('10002', 'This is Order 10002', 2) GO INSERT INTO [ORDER] ([OrderNumber],[OrderDescription],[CustomerId]) VALUES ('10003', 'This is Order 10003', 3) GO --ORDER_DETAIL INSERT INTO [ORDER_DETAIL] ([OrderId],[ProductId]) VALUES (1, 1) GO INSERT INTO [ORDER_DETAIL] ([OrderId],[ProductId]) VALUES (1, 2) GO INSERT INTO [ORDER_DETAIL] ([OrderId],[ProductId]) VALUES (1, 3) GO INSERT INTO [ORDER_DETAIL] ([OrderId],[ProductId]) VALUES (2, 1) GO INSERT INTO [ORDER_DETAIL] ([OrderId],[ProductId]) VALUES (2, 2) GO INSERT INTO [ORDER_DETAIL] ([OrderId],[ProductId]) VALUES (3, 3) GO INSERT INTO [ORDER_DETAIL] ([OrderId],[ProductId]) VALUES (3, 1) GO INSERT INTO [ORDER_DETAIL] ([OrderId],[ProductId]) VALUES (3, 2) GO INSERT INTO [ORDER_DETAIL] ([OrderId],[ProductId]) VALUES (3, 3)



GO

ExecutingthefollowingQueriesthengives:

select * from CUSTOMER

select * from PRODUCT

select * from [ORDER]

select * from ORDER_DETAIL



10.1 ExercisesRunthequeriesabovefromLabVIEW.

56

11 CreatingandUsingViews

Indatabasetheory,aviewconsistsofastoredqueryaccessibleasavirtualtablecomposedoftheresultsetofaquery.Unlikeordinarytablesinarelationaldatabase,aviewdoesnotformpartofthephysicalschema:itisadynamic,virtualtablecomputedorcollatedfromdatainthedatabase.Changingthedatainatablealtersthedatashowninsubsequentinvocationsoftheview.

Viewscanprovideadvantagesovertables:

• Viewscanrepresentasubsetofthedatacontainedinatable • Viewscanjoinandsimplifymultipletablesintoasinglevirtualtable • Viewscanactasaggregatedtables,wherethedatabaseengineaggregatesdata

(sum,averageetc)andpresentsthecalculatedresultsaspartofthedata • Viewscanhidethecomplexityofdata;forexampleaviewcouldappearasSales2000

orSales2001,transparentlypartitioningtheactualunderlyingtable • Viewstakeverylittlespacetostore;thedatabasecontainsonlythedefinitionofa

view,notacopyofallthedataitpresents • DependingontheSQLengineused,viewscanprovideextrasecurity • Viewscanlimitthedegreeofexposureofatableortablestotheouterworld

Justasfunctions(inprogramming)canprovideabstraction,sodatabaseuserscancreateabstractionbyusingviews.Inanotherparallelwithfunctions,databaseuserscanmanipulatenestedviews,thusoneviewcanaggregatedatafromotherviews.

Syntax:

CREATE VIEW <ViewName> AS …

CreateaVIEW:

Step1:CreateanewView



Step2:Addyourtables

Step3:Addyourcolumns



Step4:Saveit

UsingtheVIEWinaQuery:



11.1 ExercisesCreateasimpleviewbasedontheexampletablesandruntheviewfromLabVIEW.

60

12 CreatingandusingStoredProcedures

Astoredprocedureisasubroutineavailabletoapplicationsaccessingarelationaldatabasesystem.Typicalusesforstoredproceduresincludedatavalidation(integratedintothedatabase)oraccesscontrolmechanisms.Furthermore,storedproceduresareusedtoconsolidateandcentralizelogicthatwasoriginallyimplementedinapplications.LargeorcomplexprocessingthatmightrequiretheexecutionofseveralSQLstatementsismovedintostoredprocedures,andallapplicationscalltheproceduresonly.

AstoredprocedureisaprecompiledcollectionofSQLstatementsandoptionalcontrol-of-flowstatements,similartoamacro.Eachdatabaseanddataprovidersupportsstoredproceduresdifferently.Storedproceduresofferthefollowingbenefitstoyourdatabaseapplications:

Performance—StoredProceduresareusuallymoreefficientandfasterthanregularSQLqueriesbecauseSQLstatementsareparsedforsyntacticalaccuracyandprecompiledbytheDBMSwhenthestoredprocedureiscreated.Also,combiningalargenumberofSQLstatementswithconditionallogicandparametersintoastoredprocedureallowstheprocedurestoperformqueries,makedecisions,andreturnresultswithoutextratripstothedatabaseserver.

Maintainability—StoredProceduresisolatethelower-leveldatabasestructurefromtheapplication.Aslongasthetablenames,columnnames,parameternames,andtypesdonotchangefromwhatisstatedinthestoredprocedure,youdonotneedtomodifytheprocedurewhenchangesaremadetothedatabaseschema.StoredproceduresarealsoawaytosupportmodularSQLprogrammingbecauseafteryoucreateaprocedure,youandotheruserscanreusethatprocedurewithoutknowingthedetailsofthetablesinvolved.

Security—Whencreatingtablesinadatabase,theDatabaseAdministratorcansetEXECUTEpermissionsonstoredprocedureswithoutgrantingSELECT,INSERT,UPDATE,andDELETEpermissionstousers.Therefore,thedatainthesetablesisprotectedfromuserswhoarenotusingthestoredprocedures.

Storedproceduresaresimilartouser-definedfunctions.ThemajordifferenceisthatfunctionscanbeusedlikeanyotherexpressionwithinSQLstatements,whereasstoredproceduresmustbeinvokedusingtheCALLstatement.



ThesyntaxforcreatingaStoredProcedureisasfollows:

CREATE PROCEDURE <ProcedureName> @<Parameter1> <datatype> …

Example:CreateaStoredProcedure

ThisProceduregetsCustomerDatabasedonaspecificOrderNumber.

IF EXISTS (SELECT name FROM sysobjects WHERE name = 'sp_CustomerOrders' AND type = 'P') DROP PROCEDURE sp_CustomerOrders GO CREATE PROCEDURE sp_CustomerOrders @OrderNumber varchar(50) AS /*------------------------------------------------------------------------- Last Updated Date: 2009.11.03 Last Updated By: [email protected] Description: Get Customer Information from a specific Order Number -------------------------------------------------------------------------*/ SET NOCOUNT ON declare @CustomerId int select @CustomerId = CustomerId from [ORDER] where OrderNumber = @OrderNumber select CustomerId, FirstName, LastName, [Address], Phone from CUSTOMER where CustomerId=@CustomerId SET NOCOUNT OFF GO

Example:UsingaStoredProcedure

UsingtheStoredprocedurelikethis

exec sp_CustomerOrders '10002'

givesthefollowingresult:



12.1 ExercisesRuntheStoredProcedurecreatedabovefromLabVIEW.

63

13 CreatingandUsingTriggers

Adatabasetriggerisproceduralcodethatisautomaticallyexecutedinresponsetocertaineventsonaparticulartableorviewinadatabase.Thetriggerismostlyusedforkeepingtheintegrityoftheinformationonthedatabase.Forexample,whenanewrecord(representinganewworker)addedtotheemployeestable,newrecordsshouldbecreatedalsointhetablesofthetaxes,vacations,andsalaries.

Triggersarecommonlyusedto:

• preventchanges(e.g.preventaninvoicefrombeingchangedafterit'sbeenmailedout)

• logchanges(e.g.keepacopyoftheolddata) • auditchanges(e.g.keepalogoftheusersandrolesinvolvedinchanges) • enhancechanges(e.g.ensurethateverychangetoarecordistime-stampedbythe

server'sclock,nottheclient's) • enforcebusinessrules(e.g.requirethateveryinvoicehaveatleastonelineitem) • executebusinessrules(e.g.notifyamanagereverytimeanemployee'sbankaccount

numberchanges) • replicatedata(e.g.storearecordofeverychange,tobeshippedtoanotherdatabase

later) • enhanceperformance(e.g.updatetheaccountbalanceaftereverydetailtransaction,

forfasterqueries)

Themajorfeaturesofdatabasetriggers,andtheireffects,are:

• donotacceptparametersorarguments(butmaystoreaffected-dataintemporarytables)

• cannotperformcommitorrollbackoperationsbecausetheyarepartofthetriggeringSQLstatement

• cancancelarequestedoperation • cancausemutatingtableerrors,iftheyarepoorlywritten.



MicrosoftSQLServersupportstriggerseitherafterorinsteadofaninsert,update,ordeleteoperation.

Thesyntaxisasfollows:

CREATE TRIGGER <TriggerName> on <TableName> FOR INSERT, UPDATE, DELETE AS … Create your Code here GO

• Replace<TriggerName>withtheNameofyourTrigger• Replace<TableName>withtheNameofyourTable

DefinewhentheTriggershouldbeexecute

• IftheTriggershouldbeexecutedonlywhenyouinsertdataintothetable:FOR INSERT

• IftheTriggershouldbeexecutedonlywhenyouupdatedataintothetable:FOR UPDATE

• IftheTriggershouldbeexecutedonlywhenyoudeletedataintothetable:FOR DELETE

• IftheTriggershouldbeexecutedwhenyouinsertandupdatedataintothetable:FOR INSERT, UPDATE

• Etc.

Example:Trigger

TheExampleabovechangethe“below”intheTable“SCHOOL”from‘TUC’to‘TelemarkUniversityCollege’

CREATE TRIGGER CheckSchoolData on SCHOOL FOR INSERT, UPDATE AS DECLARE @SchoolName varchar(50) select @SchoolName=SchoolName from INSERTED If @SchoolName='TUC' update SCHOOL set SchoolName='Telemark University College' where SchoolName=@SchoolName GO



Note!Notetheuseofatemporarytablecalled“INSERTED”.ThistemporarytablecontainsthelastinsertedrecordintotheSCHOOLtable

Note!InSQLyoudefineavariablelikethis

DECLARE @myVariable <datatype>

Example:

DECLARE @SchoolName varchar(10)

Note!Youhavetousethesymbol“@”beforethenameofthevariable!!!

BelowweseehowwecreateaTriggerfromthe“SQLServerManagementStudio”:

CheckiftheTriggerisworkingasexpected:

Procedure:

Step1:Checkthedatainyourtablebeforeyoudoanything,e.g.:

select * from SCHOOL



Step2:Insertsometestdataintoyourtable,e.g.:

insert into SCHOOL (SchoolId, SchoolName) values (5, 'TUC')

Step3:CheckthedatahasbeenupdatedaccordingtoyourcodeintheTrigger:

select * from SCHOOL

→AsyouseethedatayouinsertedintothetablehasbeenautomaticallybeenchangedbytheTrigger

13.1 ExercisesCreateaTriggerthatadds“+47”toallPhonenumbersintheCUSTOMERtable.

TestandseeiftheTriggerworksproperlybyinsertingandupdatingsomedataintheCUSTOMERtable.

67

14 CreatingandusingFunctions

InSQLdatabases,auser-definedfunctionprovidesamechanismforextendingthefunctionalityofthedatabaseserverbyaddingafunctionthatcanbeevaluatedinSQLstatements.TheSQLstandarddistinguishesbetweenscalarandtablefunctions.Ascalarfunctionreturnsonlyasinglevalue(orNULL),whereasatablefunctionreturnsa(relational)tablecomprisingzeroormorerows,eachrowwithoneormorecolumns.

StoredProceduresvs.Functions:

• Onlyfunctionscanreturnavalue(usingtheRETURNkeyword). • StoredprocedurescanuseRETURNkeywordbutwithoutanyvaluebeingpassed[1] • FunctionscouldbeusedinSELECTstatements,providedtheydon’tdoanydata

manipulationandalsoshouldnothaveanyOUTorINOUTparameters. • Functionsmustreturnavalue,butforstoredproceduresthisisnotcompulsory. • AfunctioncanhaveonlyINparameters,whilestoredproceduresmayhaveOUTorIN

OUTparameters. • Afunctionisasubprogramwrittentoperformcertaincomputationsandreturna

singlevalue. • Astoredprocedureisasubprogramwrittentoperformasetofactions,andcan

returnmultiplevaluesusingtheOUTparameterorreturnnovalueatall.

User-definedfunctionsinSQLaredeclaredusingtheCREATEFUNCTIONstatement.

14.1 ExercisesCreateasimplefunctionthatfindsnumberoforderforaspecificcustomeranduseitinthefollowingquery:

“Select FirstName, LastName, fn_NumberOfOrders(CustomerId) from CUSTOMER”

68

15 SQLToolkitIhavemadeasimpleandeasyto-useSQLToolkit.TheSQLToolkitisavailablefordownloadfrommyBlog:http://home.hit.no/~hansha/

15.1 InstallationTheinstallationprocedureisasfollows:

1. DownloadthezipfileSQLToolkit.zipfrommyBlog2. Unzipthefile3. Copy"SQLToolkit.mnu"to...\LabVIEW2009\menus\Categories\4. Copy"SQLToolkit.llb"to...\LabVIEW2009\vi.lib\5. TheSQLToolkitisreadytouseandintheFunctionspaletteinLabVIEWanewpalette

named"SQL"willappear.

TheSQLToolkitpaletteinavailableinLabVIEW:

TheSQLToolkitcontainsthefollowingVIs:

“SQLOpen.vi”-ThisVIopenaconnectiontothedatabasespecifiedintheConnectionstring.Theconnectionstringmaybeasfollows:

“PROVIDER=SQLOLEDB; DATA SOURCE=xxx;UID=xxx;PWD=xxx;DATABASE=xxx”

Youneedtoreplacethe“xxx”withtheparametersfromyourdatabase.

69 SQLToolkit


“SQLSelect.vi”-ThisVIgetdatafromthedatabasespecifiedintheSQLQuery.Theoutputisa2Dstringarraywithdata.

“SQLExecute.vi”-ThisVIexecutesaQuerywithnoreturnData,e.g.,anINSERTstatement

“SQLClose.vi”-ThisVIClosetheconnectiontothedatabaseopenedby"SQLOpen.vi"

Twoexamplesarealsoincluded:

“SQL–Example1.vi”–Thisexampleselectsdatafromatable.Theexampleuses“SQLSelect.vi”inordertogetdatafromthedatabase.

Frontpanel:

BlockDiagram:

70 SQLToolkit


“SQL–Example2.vi”–Thisexampleinsertsdataintoatable.Theexampleuses“SQLExecute.vi”inordertoinsertdataintothedatabase.Nodataisreturned.

Frontpanel:

BlockDiagram:

Example:GetDataintoLabVIEWusingSQLToolkit

DownloadtheSQLtoolkitfromtheHomepageoftheDatabaseLabandfollowtheinstructionsintheReadMefile.

OntheFunctionspaletteonyourBlockDiagramthefollowingpaletteshouldappear:

71 SQLToolkit


HereisasimpleexampleofhowyougetdatafromthedatabaseintoLabVIEW:

Theprocedureisasfollows:

Step1:

Step2:

72 SQLToolkit


Step3and4:

Step5:

73 SQLToolkit


Step6:

Step7:

74 SQLToolkit


Step8:

Hans-PetterHalvorsen,M.Sc.

E-mail:[email protected]

Blog:http://home.hit.no/~hansha/

UniversityCollegeofSoutheastNorway

www.usn.no

Tutorial: Database Communication in LabVIEW

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