Structured Query Language...Structured Query Language (SQL) 3.2 Create Tables using the Designer...

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StructuredQueryLanguageHans-PetterHalvorsen

StructuredQueryLanguage

Hans-PetterHalvorsen

Copyright©2017


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TableofContents1 IntroductiontoSQL...........................................................................................................6

1.1 DataDefinitionLanguage(DDL)..................................................................................8

1.2 DataManipulationLanguage(DML)...........................................................................8

2 IntroductiontoSQLServer................................................................................................9

2.1 SQLServerManagementStudio...............................................................................10

2.1.1 CreateanewDatabase......................................................................................11

2.1.2 Queries..............................................................................................................12

3 CREATETABLE.................................................................................................................13

3.1 DatabaseModelling..................................................................................................15

3.2 CreateTablesusingtheDesignerTools....................................................................17

3.3 SQLConstraints.........................................................................................................17

3.3.1 PRIMARYKEY.....................................................................................................18

3.3.2 FOREIGNKEY.....................................................................................................19

3.3.3 NOTNULL/RequiredColumns.........................................................................22

3.3.4 UNIQUE.............................................................................................................23

3.3.5 CHECK................................................................................................................25

3.3.6 DEFAULT............................................................................................................27

3.3.7 AUTOINCREMENTorIDENTITY.........................................................................28

3.4 ALTERTABLE.............................................................................................................29

4 INSERTINTO....................................................................................................................31

5 UPDATE...........................................................................................................................33

4 TableofContents

StructuredQueryLanguage(SQL)

6 DELETE.............................................................................................................................35

7 SELECT.............................................................................................................................37

7.1 TheORDERBYKeyword............................................................................................39

7.2 SELECTDISTINCT.......................................................................................................40

7.3 TheWHEREClause....................................................................................................40

7.3.1 Operators..........................................................................................................41

7.3.2 LIKEOperator....................................................................................................41

7.3.3 INOperator........................................................................................................42

7.3.4 BETWEENOperator...........................................................................................42

7.4 Wildcards..................................................................................................................42

7.5 AND&OROperators................................................................................................43

7.6 SELECTTOPClause....................................................................................................44

7.7 Alias..........................................................................................................................45

7.8 Joins..........................................................................................................................45

7.8.1 DifferentSQLJOINs...........................................................................................46

8 SQLScripts.......................................................................................................................48

8.1 UsingComments.......................................................................................................48

8.1.1 Single-linecomment..........................................................................................48

8.1.2 Multiple-linecomment......................................................................................48

8.2 Variables...................................................................................................................49

8.3 Built-inGlobalVariables...........................................................................................50

8.3.1 @@IDENTITY.....................................................................................................50

8.4 FlowControl.............................................................................................................51

8.4.1 IF–ELSE.............................................................................................................51

8.4.2 WHILE................................................................................................................52

8.4.3 CASE...................................................................................................................53

5 TableofContents


8.4.4 CURSOR.............................................................................................................54

9 Views...............................................................................................................................56

9.1 UsingtheGraphicalDesigner...................................................................................57

10 StoredProcedures........................................................................................................61

10.1 NOCOUNTON/NOCOUNTOFF..............................................................................64

11 Functions......................................................................................................................66

11.1 Built-inFunctions..................................................................................................66

11.1.1 StringFunctions.............................................................................................66

11.1.2 DateandTimeFunctions...............................................................................67

11.1.3 MathematicsandStatisticsFunctions...........................................................67

11.1.4 AVG()..............................................................................................................68

11.1.5 COUNT().........................................................................................................68

11.1.6 TheGROUPBYStatement..............................................................................69

11.1.7 TheHAVINGClause........................................................................................70

11.2 User-definedFunctions.........................................................................................71

12 Triggers.........................................................................................................................72

13 CommunicationfromotherApplications.....................................................................75

13.1 ODBC.....................................................................................................................75

13.2 MicrosoftExcel......................................................................................................76

14 References....................................................................................................................78

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1 IntroductiontoSQLSQL(StructuredQueryLanguage)isadatabasecomputerlanguagedesignedformanagingdatainrelationaldatabasemanagementsystems(RDBMS).

SQL,isastandardizedcomputerlanguagethatwasoriginallydevelopedbyIBMforquerying,alteringanddefiningrelationaldatabases,usingdeclarativestatements.

SQLispronounced/ˌɛskjuːˈɛl/ (letterbyletter) or/ˈsiːkwəl/ (asaword).

WhatcanSQLdo?

• SQLcanexecutequeriesagainstadatabase• SQLcanretrievedatafromadatabase• SQLcaninsertrecordsinadatabase• SQLcanupdaterecordsinadatabase• SQLcandeleterecordsfromadatabase

7 IntroductiontoSQL


• SQLcancreatenewdatabases• SQLcancreatenewtablesinadatabase• SQLcancreatestoredproceduresinadatabase• SQLcancreateviewsinadatabase• SQLcansetpermissionsontables,procedures,andviews

EvenifSQLisastandard,manyofthedatabasesystemsthatexisttodayimplementtheirownversionoftheSQLlanguage.Inthisdocument,wewillusetheMicrosoftSQLServerasanexample.

Therearelotsofdifferentdatabasesystems,orDBMS–DatabaseManagementSystems,suchas:

• MicrosoftSQLServero Enterprise,Developerversions,etc.o Expressversionisfreeofcharge

• Oracle• MySQL(Oracle,previouslySunMicrosystems)-MySQLcanbeusedfreeofcharge

(opensourcelicense),WebsitesthatuseMySQL:YouTube,Wikipedia,Facebook• MicrosoftAccess• IBMDB2• Sybase• …lotsofothersystems

InthisTutorial,wewillfocusonMicrosoftSQLServer.SQLServerusesT-SQL(Transact-SQL).T-SQLisMicrosoft'sproprietaryextensiontoSQL.T-SQLisverysimilartostandardSQL,butinadditionitsupportssomeextrafunctionality,built-infunctions,etc.

8 IntroductiontoSQL


OtherusefulTutorialsaboutdatabases:

• IntroductiontoDatabaseSystems• DatabaseCommunicationinLabVIEW

TheseTutorialsarelocatedat:https://www.halvorsen.blog

1.1 DataDefinitionLanguage(DDL)TheDataDefinitionLanguage(DDL)managestableandindexstructure.ThemostbasicitemsofDDLaretheCREATE,ALTER,RENAMEandDROPstatements:

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

acolumntoanexistingtable.

1.2 DataManipulationLanguage(DML)TheDataManipulationLanguage(DML)isthesubsetofSQLusedtoadd,updateanddeletedata.

TheacronymCRUDreferstoallofthemajorfunctionsthatneedtobeimplementedinarelationaldatabaseapplicationtoconsideritcomplete.EachletterintheacronymcanbemappedtoastandardSQLstatement:

Operation SQL DescriptionCreate INSERTINTO insertsnewdataintoa

databaseRead(Retrieve) SELECT extractsdatafromadatabaseUpdate UPDATE updatesdatainadatabaseDelete(Destroy) DELETE deletesdatafromadatabase

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2 IntroductiontoSQLServerMicrosoftisthevendorofSQLServer.

WehavedifferenteditionsofSQLServer,whereSQLServerExpressisfreetodownloadanduse.

SQLServerusesT-SQL(Transact-SQL).T-SQLisMicrosoft'sproprietaryextensiontoSQL.T-SQLisverysimilartostandardSQL,butinadditionitsupportssomeextrafunctionality,built-infunctions,etc.T-SQLexpandsontheSQLstandardtoincludeproceduralprogramming,localvariables,varioussupportfunctionsforstringprocessing,dateprocessing,mathematics,etc.

SQLServerconsistsofaDatabaseEngineandaManagementStudio(andlotsofotherstuffwhichwewillnotmentionhere).TheDatabaseenginehasnographicalinterface-itisjustaservicerunninginthebackgroundofyourcomputer(preferableontheserver).TheManagementStudioisgraphicaltoolforconfiguringandviewingtheinformationinthedatabase.Itcanbeinstalledontheserverorontheclient(orboth).

10 IntroductiontoSQLServer


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

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

WhencreatingSQLcommandsandqueries,the“QueryEditor”(select“NewQuery”fromtheToolbar)isused(showninthefigureabove).

WithSQLandthe“QueryEditor”wecandoalmosteverythingwithcode,butsometimesitisalsoagoodideatousethedifferentDesignertoolsinSQLtohelpusdotheworkwithoutcoding(somuch).



2.1.1 CreateanewDatabase

ItisquitesimpletocreateanewdatabaseinMicrosoftSQLServer.Justright-clickonthe“Databases”nodeandselect“NewDatabase…”

Therearelotsofsettingsyoumaysetregardingyourdatabase,buttheonlyinformationyoumustfillinisthenameofyourdatabase:



YoumayalsousetheSQLlanguagetocreateanewdatabase,butsometimesitiseasiertojustusethebuilt-infeaturesintheManagementStudio.

2.1.2 Queries

InordertomakeanewSQLquery,selectthe“NewQuery”buttonfromtheToolbar.

HerewecanwriteanykindofqueriesthatissupportedbytheSQLlanguage.

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3 CREATETABLEBeforeyoustartimplementingyourtablesinthedatabase,youshouldalwaysspendsometimedesignyourtablesproperlyusingadesigntoollike,e.g.,ERwin,ToadDataModeler,PowerDesigner,Visio,etc.ThisiscalledDatabaseModeling.

TheCREATETABLEstatementisusedtocreateatableinadatabase.

Syntax:

CREATE TABLE table_name ( column_name1 data_type, column_name2 data_type, column_name3 data_type, .... )

Thedatatypespecifieswhattypeofdatathecolumncanhold.

14 CREATETABLE


Youhavespecialdatatypesfornumbers,textdates,etc.

Examples:

• Numbers:int,float• Text/Stings:varchar(X)–whereXisthelengthofthestring• Dates:datetime• etc.

Example:

Wewanttocreateatablecalled“CUSTOMER”whichhasthefollowingcolumnsanddatatypes:

CREATE TABLE CUSTOMER ( CustomerId int IDENTITY(1,1) PRIMARY KEY, CustomerNumber int NOT NULL UNIQUE, LastName varchar(50) NOT NULL, FirstName varchar(50) NOT NULL, AreaCode int NULL, Address varchar(50) NULL, Phone varchar(50) NULL, ) GO

Bestpractice:

Whencreatingtablesyoushouldconsiderfollowingtheseguidelines:

• Tables:Useuppercaseandsingularformintablenames–notplural,e.g.,“STUDENT”(notstudents)

• Columns:UsePascalnotation,e.g.,“StudentId”• PrimaryKey:

o Ifthetablenameis“COURSE”,namethePrimaryKeycolumn“CourseId”,etc.

15 CREATETABLE


o “Always”useIntegerandIdentity(1,1)forPrimaryKeys.UseUNIQUEconstraintforothercolumnsthatneedstobeunique,e.g.RoomNumber

• SpecifyRequiredColumns(NOTNULL)–i.e.,whichcolumnsthatneedtohavedataornot

• Standardizeonfew/theseDataTypes:int,float,varchar(x),datetime,bit• UseEnglishfortableandcolumnnames• Avoidabbreviations!(UseRoomNumber–notRoomNo,RoomNr,...)

3.1 DatabaseModellingAsmentioninthebeginningofthechapter,youshouldalwaysstartwithdatabasemodellingbeforeyoustartimplementingthetablesinadatabasesystem.

BelowweseeadatabasemodelincreatedwithERwin.

Withthistoolwecantransferthedatabasemodelastablesintodifferentdatabasesystems,suchase.g.,SQLServer.CAERwinDataModelerCommunityEditionisfreewitha25objectslimit.IthassupportforOracle,SQLServer,MySQL,ODBCandSybase.

16 CREATETABLE


BelowweseethesametablesinsidethedesigntoolinSQLServer.

17 CREATETABLE


3.2 CreateTablesusingtheDesignerToolsEvenifyoucando“everything”usingtheSQLlanguage,itissometimeseasiertodoitinthedesignertoolsintheManagementStudioinSQLServer.

Insteadofcreatingascriptyoumayaswelleasilyusethedesignerforcreatingtables.

Step1:Select“NewTable…”:

Step2:Next,thetabledesignerpopsupwhereyoucanaddcolumns,datatypes,etc.

InthisdesignerwemayalsospecifyColumnNames,DataTypes,etc.

Step3:SavethetablebyclickingtheSavebutton.

3.3 SQLConstraintsConstraintsareusedtolimitthetypeofdatathatcangointoatable.

18 CREATETABLE


Constraintscanbespecifiedwhenatableiscreated(withtheCREATETABLEstatement)orafterthetableiscreated(withtheALTERTABLEstatement).

Herearethemostimportantconstraints:

• PRIMARYKEY• NOTNULL• UNIQUE• FOREIGNKEY• CHECK• DEFAULT• IDENTITY

Inthesectionsbelowwewillexplainsomeoftheseindetail.

3.3.1 PRIMARYKEY

ThePRIMARYKEYconstraintuniquelyidentifieseachrecordinadatabasetable.

Primarykeysmustcontainuniquevalues.Itisnormaltojustuserunningnumbers,like1,2,3,4,5,…asvaluesinPrimaryKeycolumn.ItisagoodideatoletthesystemhandlethisforyoubyspecifyingthatthePrimaryKeyshouldbesettoidentity(1,1).IDENTITY(1,1)meansthefirstvaluewillbe1andthenitwillincrementby1.

Eachtableshouldhaveaprimarykey,andeachtablecanhaveonlyONEprimarykey.

IfwetakeacloserlookattheCUSTOMERtablecreatedearlier:

CREATE TABLE [CUSTOMER] ( CustomerId int IDENTITY(1,1) PRIMARY KEY, CustomerNumber int NOT NULL UNIQUE, LastName varchar(50) NOT NULL, FirstName varchar(50) NOT NULL, AreaCode int NULL, Address varchar(50) NULL, Phone varchar(50) NULL, ) GO

Asyouseeweusethe“PrimaryKey”keywordtospecifythatacolumnshouldbethePrimaryKey.

19 CREATETABLE


SettingPrimaryKeysintheDesignerTools:

IfyouusetheDesignertoolsinSQLServer,youcaneasilysettheprimaryKeyinatablejustbyright-clickandselect“SetprimaryKey”.

TheprimaryKeycolumnwillthenhaveasmallkey infronttoillustratethatthiscolumnisaPrimaryKey.

3.3.2 FOREIGNKEY

AFOREIGNKEYinonetablepointstoaPRIMARYKEYinanothertable.

Example:

WewillcreateaCREATETABLEscriptforthesetables:

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SCHOOL:

CREATE TABLE SCHOOL ( SchoolId int IDENTITY(1,1) PRIMARY KEY, SchoolName varchar(50) NOT NULL UNIQUE, Description varchar(1000) NULL, Address varchar(50) NULL, Phone varchar(50) NULL, PostCode varchar(50) NULL, PostAddress varchar(50) NULL, ) GO

CLASS:

CREATE TABLE CLASS ( ClassId int IDENTITY(1,1) PRIMARY KEY, SchoolId int NOT NULL FOREIGN KEY REFERENCES SCHOOL (SchoolId), ClassName varchar(50) NOT NULL UNIQUE, Description varchar(1000) NULL, ) GO

TheFOREIGNKEYconstraintisusedtopreventactionsthatwoulddestroylinksbetweentables.

TheFOREIGNKEYconstraintalsopreventsthatinvaliddatafrombeinginsertedintotheforeignkeycolumn,becauseithastobeoneofthevaluescontainedinthetableitpointsto.

SettingForeignKeysintheDesignerTools:

Ifyouwanttousethedesigner,right-clickonthecolumnthatyouwanttobetheForeignKeyandselect“Relationships…”:

21 CREATETABLE


Thefollowingwindowpopsup(ForeignKeyRelationships):

Clickonthe“Add”buttonandthenclickonthesmall“…”button.Thenthefollowingwindowpopsup(TablesandColumns):

22 CREATETABLE


HereyouspecifytheprimaryKeyColumninthePrimaryKeytableandtheForeignKeyColumnintheForeignKeytable.

3.3.3 NOTNULL/RequiredColumns

TheNOTNULLconstraintenforcesacolumntoNOTacceptNULLvalues.

TheNOTNULLconstraintenforcesafieldtoalwayscontainavalue.Thismeansthatyoucannotinsertanewrecord,orupdatearecordwithoutaddingavaluetothisfield.


CREATE TABLE [CUSTOMER] ( CustomerId int IDENTITY(1,1) PRIMARY KEY, CustomerNumber int NOT NULL UNIQUE, LastName varchar(50) NOT NULL, FirstName varchar(50) NOT NULL, AreaCode int NULL, Address varchar(50) NULL, Phone varchar(50) NULL, ) GO

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Weseethat“CustomerNumber”,“LastName”and“FirstName”issetto“NOTNULL”,thismeansthesecolumnsneedstocontaindata.While“AreaCode”,“Address”and“Phone”maybeleftempty,i.e,theydon’tneedtobefilledout.

Note!AprimarykeycolumncannotcontainNULLvalues.

SettingNULL/NOTNULLintheDesignerTools:

IntheTableDesigneryoucaneasilysetwhichcolumnsthatshouldallowNULLornot:

3.3.4 UNIQUE

TheUNIQUEconstraintuniquelyidentifieseachrecordinadatabasetable.TheUNIQUEandPRIMARYKEYconstraintsbothprovideaguaranteeforuniquenessforacolumnorsetofcolumns.

APRIMARYKEYconstraintautomaticallyhasaUNIQUEconstraintdefinedonit.

Note!YoucanhavemanyUNIQUEconstraintspertable,butonlyonePRIMARYKEYconstraintpertable.


CREATE TABLE [CUSTOMER] ( CustomerId int IDENTITY(1,1) PRIMARY KEY, CustomerNumber int NOT NULL UNIQUE, LastName varchar(50) NOT NULL, FirstName varchar(50) NOT NULL, AreaCode int NULL, Address varchar(50) NULL,

24 CREATETABLE


Phone varchar(50) NULL, ) GO

Weseethatthe“CustomerNumber”issettoUNIQUE,meaningeachcustomermusthaveauniqueCustomerNumber.Example:

SettingUNIQUEintheDesignerTools:

Ifyouwanttousethedesigner,right-clickonthecolumnthatyouwanttobeUNIQUEandselect“Indexes/Keys…”:

Thenclick“Add”andthensetthe“IsUnique”propertyto“Yes”:

25 CREATETABLE


3.3.5 CHECK

TheCHECKconstraintisusedtolimitthevaluerangethatcanbeplacedinacolumn.

IfyoudefineaCHECKconstraintonasinglecolumnitallowsonlycertainvaluesforthiscolumn.

IfyoudefineaCHECKconstraintonatableitcanlimitthevaluesincertaincolumnsbasedonvaluesinothercolumnsintherow.

Example:

CREATE TABLE [CUSTOMER] ( CustomerId int IDENTITY(1,1) PRIMARY KEY, CustomerNumber int NOT NULL UNIQUE CHECK(CustomerNumber>0), LastName varchar(50) NOT NULL, FirstName varchar(50) NOT NULL, AreaCode int NULL, Address varchar(50) NULL, Phone varchar(50) NULL, ) GO

Inthiscase,whenwetrytoinsertaCustomerNumberlessthanzerowewillgetanerrormessage.

SettingCHECKconstraintsintheDesignerTools:

Ifyouwanttousethedesigner,right-clickonthecolumnwhereyouwanttosettheconstraintsandselect“CheckConstraints…”:

26 CREATETABLE


Thenclick“Add”andthenclick“…”inordertoopentheExpressionwindow:

IntheExpressionwindowyoucantypeintheexpressionyouwanttouse:

27 CREATETABLE


3.3.6 DEFAULT

TheDEFAULTconstraintisusedtoinsertadefaultvalueintoacolumn.

Thedefaultvaluewillbeaddedtoallnewrecords,ifnoothervalueisspecified.

Example:

CREATE TABLE [CUSTOMER] ( CustomerId int IDENTITY(1,1) PRIMARY KEY, CustomerNumber int NOT NULL UNIQUE, LastName varchar(50) NOT NULL, FirstName varchar(50) NOT NULL, Country varchar(20) DEFAULT 'Norway',

AreaCode int NULL, Address varchar(50) NULL, Phone varchar(50) NULL, ) GO

SettingDEFAULTvaluesintheDesignerTools:

Selectthecolumnandgointothe“ColumnProperties”:

28 CREATETABLE


3.3.7 AUTOINCREMENTorIDENTITY

Veryoftenwewouldlikethevalueoftheprimarykeyfieldtobecreatedautomaticallyeverytimeanewrecordisinserted.

Example:

CREATE TABLE CUSTOMER ( CustomerId int IDENTITY(1,1) PRIMARY KEY, CustomerNumber int NOT NULL UNIQUE, LastName varchar(50) NOT NULL, FirstName varchar(50) NOT NULL, AreaCode int NULL, Address varchar(50) NULL, Phone varchar(50) NULL, ) GO

Asshownbelow,weusetheIDENTITY()forthis.IDENTITY(1,1)meansthefirstvaluewillbe1andthenitwillincrementby1.

Settingidentity(1,1)intheDesignerTools:

WecanusethedesignertoolstospecifythataPrimaryKeyshouldbeanidentitycolumnthatisautomaticallygeneratedbythesystemwhenweinsertdataintothetable.

ClickonthecolumninthedesignerandgointotheColumnPropertieswindow:

29 CREATETABLE


3.4 ALTERTABLETheALTERTABLEstatementisusedtoadd,delete,ormodifycolumnsinanexistingtable.

Toaddacolumninatable,usethefollowingsyntax:

ALTER TABLE table_name ADD column_name datatype

Todeleteacolumninatable,usethefollowingsyntax(noticethatsomedatabasesystemsdon'tallowdeletingacolumn):

ALTER TABLE table_name DROP COLUMN column_name

Tochangethedatatypeofacolumninatable,usethefollowingsyntax:

ALTER TABLE table_name ALTER COLUMN column_name datatype

IfweuseCREATETABLEandthetablealreadyexistsinthetablewewillgetanerrormessage,soifwecombineCREATETABLEandALTERTABLEwecancreaterobustdatabasescriptsthatgivesnoerrors,astheexampleshownbelow:

if not exists (select * from dbo.sysobjects where id = object_id(N'[CUSTOMER]') and OBJECTPROPERTY(id, N'IsUserTable') = 1) CREATE TABLE CUSTOMER ( CustomerId int PRIMARY KEY, CustomerNumber int NOT NULL UNIQUE, LastName varchar(50) NOT NULL, FirstName varchar(50) NOT NULL, AreaCode int NULL, Address varchar(50) NULL, Phone varchar(50) NULL, ) GO if exists(select * from dbo.syscolumns where id = object_id(N'[CUSTOMER]') and OBJECTPROPERTY(id, N'IsUserTable') = 1 and name = 'CustomerId') ALTER TABLE CUSTOMER ALTER COLUMN CustomerId int Else ALTER TABLE CUSTOMER ADD CustomerId int GO if exists(select * from dbo.syscolumns where id = object_id(N'[CUSTOMER]') and OBJECTPROPERTY(id, N'IsUserTable') = 1 and name = 'CustomerNumber') ALTER TABLE CUSTOMER ALTER COLUMN CustomerNumber int

30 CREATETABLE


Else ALTER TABLE CUSTOMER ADD CustomerNumber int GO ...

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4 INSERTINTOTheINSERTINTOstatementisusedtoinsertanewrowinatable.

ItispossibletowritetheINSERTINTOstatementintwoforms.

Thefirstformdoesn'tspecifythecolumnnameswherethedatawillbeinserted,onlytheirvalues:

INSERT INTO table_name VALUES (value1, value2, value3,...)

Example:

INSERT INTO CUSTOMER VALUES ('1000', 'Smith', 'John', 12, 'California', '11111111')

Thesecondformspecifiesboththecolumnnamesandthevaluestobeinserted:

INSERT INTO table_name (column1, column2, column3,...) VALUES (value1, value2, value3,...)

Thisformisrecommended!

Example:

INSERT INTO CUSTOMER (CustomerNumber, LastName, FirstName, AreaCode, Address, Phone) VALUES ('1000', 'Smith', 'John', 12, 'California', '11111111')

InsertDataOnlyinSpecifiedColumns:

Itisalsopossibletoonlyadddatainspecificcolumns.

Example:

INSERT INTO CUSTOMER (CustomerNumber, LastName, FirstName) VALUES ('1000', 'Smith', 'John')

Note!YouneedatleasttoincludeallcolumnsthatcannotbeNULL.

WerememberthetabledefinitionfortheCUSTOMERtable:

32 INSERTINTO


i.e.,weneedtoincludeatleast“CustomerNumber”,“LastName”and“FirstName”.“CustomerId”issetto“identity(1,1)”andthereforevaluesforthiscolumnaregeneratedbythesystem.

InsertDataintheDesignerTools:

Whenyouhavecreatedthetables,youcaneasilyinsertdataintothemusingthedesignertools.Right-clickonthespecifictableandselect“EditTop200Rows”:

Thenyoucanenterdatainatableformat,similarto,e.g.,MSExcel:

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5 UPDATETheUPDATEstatementisusedtoupdateexistingrecordsinatable.

Thesyntaxisasfollows:

UPDATE table_name SET column1=value, column2=value2,... WHERE some_column=some_value

Note!NoticetheWHEREclauseintheUPDATEsyntax.TheWHEREclausespecifieswhichrecordorrecordsthatshouldbeupdated.IfyouomittheWHEREclause,allrecordswillbeupdated!

Example:

update CUSTOMER set AreaCode=46 where CustomerId=2

Beforeupdate:

Afterupdate:

Ifyoudon’tincludetheWHEREclausetheresultbecomes:

→SomakesuretoincludetheWHEREclausewhenusingtheUPDATEcommand!

34 UPDATE


UpdateDataintheDesignerTools:

Thesamewayyouinsertdatayoucanalsoupdatethedata.Right-clickonthespecifictableandselect“EditTop200Rows”:

Thenyoucanchangeyourdata:

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6 DELETETheDELETEstatementisusedtodeleterowsinatable.

Syntax:

DELETE FROM table_name WHERE some_column=some_value

Note!NoticetheWHEREclauseintheDELETEsyntax.TheWHEREclausespecifieswhichrecordorrecordsthatshouldbedeleted.IfyouomittheWHEREclause,allrecordswillbedeleted!

Example:

delete from CUSTOMER where CustomerId=2

Beforedelete:

Afterdelete:

DeleteAllRows:

Itispossibletodeleteallrowsinatablewithoutdeletingthetable.Thismeansthatthetablestructure,attributes,andindexeswillbeintact:

DELETE FROM table_name

Note!Makesuretodothisonlywhenyoureallymeanit!YoucannotUNDOthisstatement!

DeleteDataintheDesignerTools:

Youdeletedatainthedesignerbyright-clickontherowandselect“Delete”:

36 DELETE


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7 SELECTTheSELECTstatementisprobablythemostusedSQLcommand.TheSELECTstatementisusedforretrievingrowsfromthedatabaseandenablestheselectionofoneormanyrowsorcolumnsfromoneormanytablesinthedatabase.

WewillusetheCUSTOMERtableasanexample.

TheCUSTOMERtablehasthefollowingcolumns:

TheCUSTOMERtablecontainsthefollowingdata:

Example:

select * from CUSTOMER

ThissimpleexamplegetsallthedatainthetableCUSTOMER.Thesymbol“*”isusedwhenyouwanttogetallthecolumnsinthetable.

38 SELECT


Ifyouonlywantafewcolumns,youmayspecifythenamesofthecolumnsyouwanttoretrieve,example:

select CustomerId, LastName, FirstName from CUSTOMER

SointhesimplestformwecanusetheSELECTstatementasfollows:

select <column_names> from <table_names>

Ifwewantallcolumns,weusethesymbol“*”

Note!SQLisnotcasesensitive.SELECTisthesameasselect.

ThefullsyntaxoftheSELECTstatementiscomplex,butthemainclausescanbesummarizedas:

SELECT [ ALL | DISTINCT ] [TOP ( expression ) [PERCENT] [ WITH TIES ] ] select_list [ INTO new_table ] [ FROM table_source ] [ WHERE search_condition ] [ GROUP BY group_by_expression ] [ HAVING search_condition ] [ ORDER BY order_expression [ ASC | DESC ] ]

Itseemscomplex,butwewilltakethedifferentpartsstepbystepinthenextsections.

SelectDataintheDesignerTools:

Right-clickonatableandselect“SelectTop1000Rows”:

Thefollowingwillappear:

39 SELECT


ASelectqueryisautomaticallycreatedforyouwhichyoucaneditifyouwantto.

7.1 TheORDERBYKeywordIfyouwantthedatatoappearinaspecificorderyouneedtousethe“orderby”keyword.

Example:

select * from CUSTOMER order by LastName

Youmayalsosortbyseveralcolumns,e.g.likethis:

select * from CUSTOMER order by Address, LastName

Ifyouusethe“orderby”keyword,thedefaultorderisascending(“asc”).Ifyouwanttheordertobeopposite,i.e.,descending,thenyouneedtousethe“desc”keyword.

40 SELECT


select * from CUSTOMER order by LastName desc

7.2 SELECTDISTINCTInatable,someofthecolumnsmaycontainduplicatevalues.Thisisnotaproblem,however,sometimesyouwillwanttolistonlythedifferent(distinct)valuesinatable.

TheDISTINCTkeywordcanbeusedtoreturnonlydistinct(different)values.


select distinct <column_names> from <table_names>

Example:

select distinct FirstName from CUSTOMER

7.3 TheWHEREClauseTheWHEREclauseisusedtoextractonlythoserecordsthatfulfillaspecifiedcriterion.


select <column_names> from <table_name> where <column_name> operator value

Example:

select * from CUSTOMER where CustomerNumber='1001'

41 SELECT


Note!SQLusessinglequotesaroundtextvalues,asshownintheexampleabove.

7.3.1 Operators

WiththeWHEREclause,thefollowingoperatorscanbeused:

Operator Description= Equal<> Notequal > Greaterthan < Lessthan >= Greaterthanorequal <= Lessthanorequal BETWEEN Betweenaninclusiverange LIKE Searchforapattern IN Ifyouknowtheexactvalueyouwanttoreturnforatleastoneofthe

columns

Examples:

select * from CUSTOMER where AreaCode>30

7.3.2 LIKEOperator

TheLIKEoperatorisusedtosearchforaspecifiedpatterninacolumn.

Syntax:

SELECT column_name(s) FROM table_name WHERE column_name LIKE pattern

Example:

select * from CUSTOMER where LastName like 'J%'

Note!The"%"signcanbeusedtodefinewildcards(missinglettersinthepattern)bothbeforeandafterthepattern.

42 SELECT


select * from CUSTOMER where LastName like '%a%'

YoumayalsocombinewiththeNOTkeyword,example:

select * from CUSTOMER where LastName not like '%a%'

7.3.3 INOperator

TheINoperatorallowsyoutospecifymultiplevaluesinaWHEREclause.

Syntax:

SELECT column_name(s) FROM table_name WHERE column_name IN (value1,value2,...)

7.3.4 BETWEENOperator

TheBETWEENoperatorselectsarangeofdatabetweentwovalues.Thevaluescanbenumbers,text,ordates.

Syntax:

SELECT column_name(s) FROM table_name WHERE column_name BETWEEN value1 AND value2

7.4 WildcardsSQLwildcardscansubstituteforoneormorecharacterswhensearchingfordatainadatabase.

Note!SQLwildcardsmustbeusedwiththeSQLLIKEoperator.

WithSQL,thefollowingwildcardscanbeused:

43 SELECT


Wildcard Description% Asubstituteforzeroormorecharacters_ Asubstituteforexactlyonecharacter[charlist] Anysinglecharacterincharlist[^charlist]or[!charlist]

Anysinglecharacternotincharlist

Examples:

SELECT * FROM CUSTOMER WHERE LastName LIKE 'J_cks_n'

SELECT * FROM CUSTOMER WHERE CustomerNumber LIKE '[10]%'

7.5 AND&OROperatorsTheANDoperatordisplaysarecordifboththefirstconditionandthesecondconditionistrue.

TheORoperatordisplaysarecordifeitherthefirstconditionorthesecondconditionistrue.

Examples:

select * from CUSTOMER where LastName='Smith' and FirstName='John'

select * from CUSTOMER where LastName='Smith' or FirstName='John'

44 SELECT


CombiningAND&OR:

YoucanalsocombineANDandOR(useparenthesistoformcomplexexpressions).

Example:

select * from CUSTOMER where LastName='Smith' and (FirstName='John' or FirstName='Smith')

7.6 SELECTTOPClauseTheTOPclauseisusedtospecifythenumberofrecordstoreturn.

TheTOPclausecanbeveryusefulonlargetableswiththousandsofrecords.Returningalargenumberofrecordscanimpactonperformance.

Syntax:

SELECT TOP number|percent column_name(s) FROM table_name

Examples:

select TOP 1 * from CUSTOMER

Youcanalsospecifyinpercent:

select TOP 60 percent * from CUSTOMER

Thisisveryusefulforlargetableswiththousandsofrecords

45 SELECT


7.7 AliasYoucangiveatableoracolumnanothernamebyusinganalias.Thiscanbeagoodthingtodoifyouhaveverylongorcomplextablenamesorcolumnnames.

Analiasnamecouldbeanything,butusuallyitisshort.

SQLAliasSyntaxforTables:

SELECT column_name(s) FROM table_name AS alias_name

SQLAliasSyntaxforColumns:

SELECT column_name AS alias_name FROM table_name

7.8 JoinsSQLjoinsareusedtoquerydatafromtwoormoretables,basedonarelationshipbetweencertaincolumnsinthesetables.

46 SELECT


7.8.1 DifferentSQLJOINs

Beforewecontinuewithexamples,wewilllistthetypesofJOINyoucanuse,andthedifferencesbetweenthem.

• JOIN:Returnrowswhenthereisatleastonematchinbothtables• LEFTJOIN:Returnallrowsfromthelefttable,eveniftherearenomatchesinthe

righttable• RIGHTJOIN:Returnallrowsfromtherighttable,eveniftherearenomatchesinthe

lefttable• FULLJOIN:Returnrowswhenthereisamatchinoneofthetables

Example:

Given2tables:

• SCHOOL• CLASS

47 SELECT


Thediagramisshownbelow:

Wewanttogetthefollowinginformationusingaquery:

SchoolName ClassName

… …

… …

InordertogetinformationfrommorethanonetableweneedtousetheJOIN.TheJOINisusedtojointheprimarykeyinonetablewiththeforeignkeyinanothertable.

select SCHOOL.SchoolName, CLASS.ClassName from SCHOOL INNER JOIN CLASS ON SCHOOL.SchoolId = CLASS.SchoolId

48

8 SQLScriptsASQLscriptisacollectionofSQLstatementsthatyoucanexecuteinoneoperation.YoucanuseanykindofSQLcommands,suchasinsert,select,delete,update,etc.Inadditionyoucandefineandusevariables,andyoumayalsouseprogramflowlikeIf-Else,etc.Youmayalsoaddcommentstomakethescripteasiertoreadandunderstand.

8.1 UsingCommentsUsingcommentsinyouSQLscriptisimportanttomakethescripteasiertoreadandunderstand.

InSQLwecanuse2differentkindsofcomments:

• Single-linecomment• Multiple-linecomment

8.1.1 Single-linecomment

Wecancommentonelineatthetimeusing“--”beforethetextyouwanttocommentout.

Syntax:

-- text_of_comment

8.1.2 Multiple-linecomment

Wecancommentseverallineusing“/*”inthestartofthecommentand“*/”intheendofthecomment.

Syntax:

/* text_of_comment text_of_comment */

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8.2 VariablesTheabilitytousingvariablesinSQLisapowerfulfeature.YouneedtousethekeywordDECLAREwhenyouwanttodefinethevariables.Localvariablesmusthavethethesymbol“@”asaprefix.Youalsoneedtospecifyadatatypeforyourvariable(int,varchar(x),etc.).

Syntaxfordeclaringvariables:

declare @local_variable data_type

Ifyouhavemorethanonevariableyouwanttodeclare:

declare @myvariable1 data_type, @myvariable2 data_type, …

Whenyouwanttoassignvaluestothevariable,youmustuseeitheraSEToraSELECTstatement.

Example:

declare @myvariable int set @myvariable=4

Ifyouwanttoseethevalueforavariable,youcane.g.,usethePRINTcommandlikethis:

declare @myvariable int set @myvariable=4 print @myvariable

ThefollowingwillbeshowninSQLServer:

AssigningvariableswithavaluefromaSELECTstatementisveryuseful.

50 SQLScripts


WeusetheCUSTOMERtableasanexample:

Youcanassignavaluetothevariablefromaselectstatementlikethis:

declare @mylastname varchar(50) select @mylastname=LastName from CUSTOMER where CustomerId=2 print @mylastname

YoucanalsouseavariableintheWHEREclauseLIKE,e.g.,this:

declare @find varchar(30) set @find = 'J%' select * from CUSTOMER where LastName LIKE @find

8.3 Built-inGlobalVariablesSQLhavelotsofbuilt-invariablesthatareveryusefultouseinqueriesandscripts.

8.3.1 @@IDENTITY

AfteranINSERT,SELECTINTO,orbulkcopystatementiscompleted,@@IDENTITYcontainsthelastidentityvaluethatisgeneratedbythestatement.Ifthestatementdidnotaffectanytableswithidentitycolumns,@@IDENTITYreturnsNULL.Ifmultiplerowsareinserted,generatingmultipleidentityvalues,@@IDENTITYreturnsthelastidentityvaluegenerated.

Example:

Giventotables;SCHOOLandCOURSE:

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SCHOOLtable: COURSEtable:

WewanttoinsertanewSchoolintotheSCHOOLtableandwewanttoinsert2newCoursesintheCOURSEtablethatbelongtotheSchoolweinsert.Tofindthe“SchoolId”wecanusethe@@IDENTITYvariable:

declare @SchoolId int -- Insert Data into SCHOOL table insert into SCHOOL(SchoolName) values ('MIT') select @SchoolId = @@IDENTITY -- Insert Courses for the specific School above in the COURSE table insert into COURSE(SchoolId,CourseName) values (@SchoolId, 'MIT-101') insert into COURSE(SchoolId,CourseName) values (@SchoolId, 'MIT-201')

Theresultbecomes:

SCHOOLtable: COURSEtable:

8.4 FlowControlAswithotherprogramminglanguagesyoucanusedifferentkindofflowcontrol,suchasIF-ELSE,WHILE,etc,whichisveryuseful.

8.4.1 IF–ELSE

TheIF-ELSEisveryuseful.Belowweseeanexample:

declare @customerNumber int

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select @customerNumber=CustomerNumber from CUSTOMER where CustomerId=2 if @customerNumber > 1000 print 'The Customer Number is larger than 1000' else print 'The Customer Number is not larger than 1000'

BEGIN…END:

IfmorethanonelineofcodeistobeexecutedwithinanIFsentenceyouneedtouseBEGIN…END.

Example:

select @customerNumber=CustomerNumber from CUSTOMER where CustomerId=2 if @customerNumber > 1000 begin print 'The Customer Number is larger than 1000' update CUSTOMER set AreaCode=46 where CustomerId=2 end else print 'The Customer Number is not larger than 1000'

8.4.2 WHILE

WecanalsouseWHILE,whichisknownfromotherprogramminglanguages.

Example:

WeareusingtheCUSTOMERtable:

andthefollowingquery:

while (select AreaCode from CUSTOMER where CustomerId=1) < 20 begin update CUSTOMER set AreaCode = AreaCode + 1

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end select * from CUSTOMER

AsyoucanseethecodeinsidetheWHILEloopisexecutedaslongas“AreaCode”forCustomerId=1islessthan20.Foreachiterationisthe“AreaCode”forthatcustomerincrementedwith1.

8.4.3 CASE

TheCASEstatementevaluatesalistofconditionsandreturnsoneofmultiplepossibleresultexpressions.

Example:

Wehavea“GRADE”tablethatcontainsthegradesforeachstudentindifferentcourses:

select GradeId, StudentId, CourseId, Grade from GRADE

Inthe“GRADE”tableisthegradesstoredasnumbers,butsincethestudentsgetgradeswiththelettersA..F(A=5,B=4,C=3,D=2,E=1,F=0),wewanttoconvertthevaluesinthetableintolettersusingaCASEstatement:

select GradeId, StudentId, CourseId, case Grade when 5 then 'A' when 4 then 'B' when 3 then 'C' when 2 then 'D' when 1 then 'E' when 0 then 'F'

else '-' end as Grade from

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GRADE

8.4.4 CURSOR

Inadvancesscripts,CURSORsmaybeveryuseful.ACURSORworkslikeanadvancedWHILEloopwhichweusetoiteratethroughtherecordsinoneormoretables.

CURSORSareusedmainlyinstoredprocedures,triggers,andSQLscripts.

Example:


WewillcreateaCURSORthatiteratethroughalltherecordsintheCUSTOMERtableandcheckifthePhonenumberconsistsof8digits,ifnotthescriptwillreplacetheinvalidPhonenumberwiththetext“Phonenumberisnotvalid”.

HereistheSQLScriptusingaCURSOR:

DECLARE @CustomerId int, @phone varchar(50) DECLARE db_cursor CURSOR FOR SELECT CustomerId from CUSTOMER OPEN db_cursor FETCH NEXT FROM db_cursor INTO @CustomerId WHILE @@FETCH_STATUS = 0 BEGIN select @phone=Phone from CUSTOMER where CustomerId=@CustomerId if LEN(@phone) < 8

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update CUSTOMER set Phone='Phone number is not valid' where CustomerId=@CustomerId FETCH NEXT FROM db_cursor INTO @CustomerId END CLOSE db_cursor DEALLOCATE db_cursor

TheCUSTOMERtablebecomes:

CreatingandusingaCURSORincludesthesesteps:

• DeclareSQLvariablestocontainthedatareturnedbythecursor.Declareonevariableforeachresultsetcolumn.

• AssociateaSQLcursorwithaSELECTstatementusingtheDECLARECURSORstatement.TheDECLARECURSORstatementalsodefinesthecharacteristicsofthecursor,suchasthecursornameandwhetherthecursorisread-onlyorforward-only.

• UsetheOPENstatementtoexecutetheSELECTstatementandpopulatethecursor.• UsetheFETCHINTOstatementtofetchindividualrowsandhavethedataforeach

columnmovedintoaspecifiedvariable.OtherSQLstatementscanthenreferencethosevariablestoaccessthefetcheddatavalues.

• Whenyouarefinishedwiththecursor,usetheCLOSEstatement.Closingacursorfreessomeresources,suchasthecursor'sresultsetanditslocksonthecurrentrow.TheDEALLOCATEstatementcompletelyfreesallresourcesallocatedtothecursor,includingthecursorname.

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9 ViewsViewsarevirtualtableforeasieraccesstodatastoredinmultipletables.

SyntaxforcreatingaView:

CREATE VIEW <ViewName> AS …

...butitmightbeeasiertodoitinthegraphicalviewdesignerthatarebuiltintoSQLManagementStudio.

SyntaxforusingaView:

select * from <MyView> where …

Asshownabove,weuseaVIEWjustlikeweuseanordinarytable.

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Example:

WeusetheSCHOOLandCLASStablesasanexampleforourView.WewanttocreateaViewthatlistsalltheexistingschoolsandthebelongingclasses.

WecreatetheVIEWusingtheCREATEVIEWcommand:

CREATE VIEW SchoolView AS SELECT SCHOOL.SchoolName, CLASS.ClassName FROM SCHOOL INNER JOIN CLASS ON SCHOOL.SchoolId = CLASS.SchoolId

Note!Inordertogetinformationfrommorethanonetable,weneedtolinkthetablestogetherusingaJOIN.

9.1 UsingtheGraphicalDesignerWecreatethesameViewusingthegraphicaldesignerinSQLServerManagementStudio:

58 Views


Step1:Right-clickontheViewnodeandselect“NewView…”:

Step2:Addnecessarytables:

59 Views


Step3:AddColumns,etc.

Step4:SavetheVIEW:

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Step5:UsetheVIEWinaquery:

select * from SchoolView

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10 StoredProceduresAStoredProcedureisaprecompiledcollectionofSQLstatements.Inastoredprocedureyoucanuseifsentence,declarevariables,etc.

SyntaxforcreatingaStoredProcedure:

CREATE PROCEDURE <ProcedureName> @<Parameter1> <datatype> … declare @myVariable <datatype> … Create your Code here

Note!Youneedtousethesymbol“@”beforevariablenames.

SyntaxforusingaStoredProcedure:

EXECUTE <ProcedureName(…)>

Example:

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WeusetheSCHOOLandCLASStablesasanexampleforourStoredProcedure.WewanttocreateaStoredProcedurethatlistsalltheexistingschoolsandthebelongingclasses.

WecreatetheStoredProcedureasfollows:

CREATE PROCEDURE GetAllSchoolClasses AS select SCHOOL.SchoolName, CLASS.ClassName from SCHOOL inner join CLASS on SCHOOL.SchoolId = CLASS.SchoolId order by SchoolName, ClassName

WhenwehavecreatedtheStoredProcedurewecanrun(orexecute)theStoredprocedureusingtheexecutecommandlikethis:

execute GetAllSchoolClasses

WecanalsocreateaStoreProcedurewithinputparameters.

Example:

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Weusethesametablesinthisexample(SCHOOLandCLASS)butnowwewanttolistallclassesforaspecificschool.

TheStoredProcedurebecomes:

CREATE PROCEDURE GetSpecificSchoolClasses @SchoolName varchar(50) AS select SCHOOL.SchoolName, CLASS.ClassName from SCHOOL inner join CLASS on SCHOOL.SchoolId = CLASS.SchoolId where SchoolName=@SchoolName order by ClassName

Werun(orexecute)theStoredProcedure:

execute GetSpecificSchoolClasses 'TUC'

or:

execute GetSpecificSchoolClasses 'NTNU'

WhenwetrytocreateaStoredProcedurethatalreadyexistswegetthefollowingerrormessage:

There is already an object named 'GetSpecificSchoolClasses' in the database.

Thenwefirstneedtodelete(orDROP)theoldStoredProcedurebeforewecanrecreateitagain.

WecandothismanuallyintheManagementStudioinSQLlikethis:

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Abettersolutionistoaddcodeforthisinourscript,likethis:

IF EXISTS (SELECT name FROM sysobjects WHERE name = GetSpecificSchoolClasses ' AND type = 'P') DROP PROCEDURE GetSpecificSchoolClasses GO CREATE PROCEDURE GetSpecificSchoolClasses @SchoolName varchar(50) AS select SCHOOL.SchoolName, CLASS.ClassName from SCHOOL inner join CLASS on SCHOOL.SchoolId = CLASS.SchoolId where SchoolName=@SchoolName order by ClassName

SoweuseCREATEPROCEDUREtocreateaStoredProcedureandweuseDROPPROCEDUREtodeleteaStoredProcedure.

10.1 NOCOUNTON/NOCOUNTOFFInadvancedStoredProceduresandScript,performanceisveryimportant.UsingSETNOCOUNTONandSETNOCOUNTOFFmakestheStoredProcedurerunfaster.

SETNOCOUNTONstopsthemessagethatshowsthecountofthenumberofrowsaffectedbyaTransact-SQLstatementorstoredprocedurefrombeingreturnedaspartoftheresultset.

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SETNOCOUNTONpreventsthesendingofDONE_IN_PROCmessagestotheclientforeachstatementinastoredprocedure.Forstoredproceduresthatcontainseveralstatementsthatdonotreturnmuchactualdata,orforproceduresthatcontainTransact-SQLloops,settingSETNOCOUNTtoONcanprovideasignificantperformanceboost,becausenetworktrafficisgreatlyreduced.

Example:

IF EXISTS (SELECT name FROM sysobjects WHERE name = 'sp_LIMS_IMPORT_REAGENT' AND type = 'P') DROP PROCEDURE sp_LIMS_IMPORT_REAGENT GO CREATE PROCEDURE sp_LIMS_IMPORT_REAGENT @Name varchar(100), @LotNumber varchar(100), @ProductNumber varchar(100), @Manufacturer varchar(100) AS SET NOCOUNT ON if not exists (SELECT ReagentId FROM LIMS_REAGENTS WHERE [Name]=@Name) INSERT INTO LIMS_REAGENTS ([Name], ProductNumber, Manufacturer) VALUES (@Name, @ProductNumber, @Manufacturer) else UPDATE LIMS_REAGENTS SET [Name] = @Name, ProductNumber = @ProductNumber, Manufacturer = @Manufacturer, WHERE [Name] = @Name SET NOCOUNT OFF GO

ThisStoredProcedureupdatesatableinthedatabaseandinthiscaseyoudon’tnormallyneedfeedback,spsettingSETNOCOUNTONatthetopinthestoredprocedureisagoodidea.itisalsogoodpracticetoSETNOCOUNTOFFatthebottomofthestoredprocedure.

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11 FunctionsWithSQLandSQLServeryoucanuselotsofbuilt-infunctionsoryoumaycreateyourownfunctions.Herewewilllearntousesomeofthemostusedbuilt-infunctionsandinadditionwewillcreateourownfunction.

11.1 Built-inFunctionsSQLhasmanybuilt-infunctionsforperformingcalculationsondata.

Wehave2categoriesoffunctions,namelyaggregatefunctionsandscalarfunctions.Aggregatefunctionsreturnasinglevalue,calculatedfromvaluesinacolumn,whilescalarfunctionsreturnasinglevalue,basedontheinputvalue.

Aggregatefunctions-examples:

• AVG()-Returnstheaveragevalue• STDEV()-Returnsthestandarddeviationvalue• COUNT()-Returnsthenumberofrows• MAX()-Returnsthelargestvalue• MIN()-Returnsthesmallestvalue• SUM()-Returnsthesum• etc.

Scalarfunctions-examples:

• UPPER()-Convertsafieldtouppercase• LOWER()-Convertsafieldtolowercase• LEN()-Returnsthelengthofatextfield• ROUND()-Roundsanumericfieldtothenumberofdecimalsspecified• GETDATE()-Returnsthecurrentsystemdateandtime• etc.

11.1.1 StringFunctions

HerearesomeusefulfunctionsusedtomanipulatewithstringsinSQLServer:

67 Functions


• CHAR • CHARINDEX • REPLACE • SUBSTRING • LEN • REVERSE • LEFT• RIGHT • LOWER • UPPER • LTRIM • RTRIM

ReadmoreaboutthesefunctionsintheSQLServerHelp.

11.1.2 DateandTimeFunctions

HerearesomeusefulDateandTimefunctionsinSQLServer:

• DATEPART• GETDATE• DATEADD• DATEDIFF• DAY• MONTH• YEAR• ISDATE


11.1.3 MathematicsandStatisticsFunctions

HerearesomeusefulfunctionsformathematicsandstatisticsinSQLServer:

• COUNT• MIN,MAX• COS,SIN,TAN• SQRT• STDEV• MEAN• AVG

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11.1.4 AVG()

TheAVG()functionreturnstheaveragevalueofanumericcolumn.

Syntax:

SELECT AVG(column_name) FROM table_name

Example:

GivenaGRADEtable:

Wewanttofindtheaveragegradeforaspecificstudent:

select AVG(Grade) as AvgGrade from GRADE where StudentId=1

11.1.5 COUNT()

TheCOUNT()functionreturnsthenumberofrowsthatmatchesaspecifiedcriteria.

TheCOUNT(column_name)functionreturnsthenumberofvalues(NULLvalueswillnotbecounted)ofthespecifiedcolumn:

SELECT COUNT(column_name) FROM table_name

TheCOUNT(*)functionreturnsthenumberofrecordsinatable:

SELECT COUNT(*) FROM table_name

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select COUNT(*) as NumbersofCustomers from CUSTOMER

11.1.6 TheGROUPBYStatement

AggregatefunctionsoftenneedanaddedGROUPBYstatement.

TheGROUPBYstatementisusedinconjunctionwiththeaggregatefunctionstogrouptheresult-setbyoneormorecolumns.

Syntax

SELECT column_name, aggregate_function(column_name) FROM table_name WHERE column_name operator value GROUP BY column_name

Example:


Ifwetrythefollowing:

select FirstName, MAX(AreaCode) from CUSTOMER

Wegetthefollowingerrormessage:

Column 'CUSTOMER.FirstName' is invalid in the select list because it is not contained in either an aggregate function or the GROUP BY clause.

ThesolutionistousetheGROUPBY:

select FirstName, MAX(AreaCode) from CUSTOMER group by FirstName

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11.1.7 TheHAVINGClause

TheHAVINGclausewasaddedtoSQLbecausetheWHEREkeywordcouldnotbeusedwithaggregatefunctions.

Syntax:

SELECT column_name, aggregate_function(column_name) FROM table_name WHERE column_name operator value GROUP BY column_name HAVING aggregate_function(column_name) operator value

WeusetheGRADEtableasanexample:

select * from GRADE

FirstweusetheGROUPBYstatement:

select CourseId, AVG(Grade) from GRADE group by CourseId

Whilethefollowingquery:

select CourseId, AVG(Grade) from GRADE group by CourseId having AVG(Grade)>3

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11.2 User-definedFunctionsINSQL,wemayalsocreateourownfunctions,so-calleduser-definedfunctions.

Auser-definedfunctionisaroutinethatacceptsparameters,performsanaction,suchasacomplexcalculation,andreturnstheresultofthatactionasavalue.Thereturnvaluecaneitherbeascalar(single)valueoratable.Usethisstatementtocreateareusableroutinethatcanbeusedinotherqueries.

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.

Whenwehavecreatedthefunction,wecanusethefunctionthesamewayweusebuilt-infunctions.

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12 TriggersAdatabasetriggeriscodethatisautomaticallyexecutedinresponsetocertaineventsonaparticulartableinadatabase.

SyntaxforcreatingaTrigger:

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

TheTriggerwillautomaticallybeexecutedwhendataisinserted,updatedordeletedinthetableasspecifiedintheTriggerheader.

INSERTEDandDELETED:

Insidetriggerswecanusetwospecialtables:theDELETEDtableandtheINSERTEDtables.SQLServerautomaticallycreatesandmanagesthesetables.Youcanusethesetemporary,

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memory-residenttablestotesttheeffectsofcertaindatamodifications.Youcannotmodifythedatainthesetables.

TheDELETEDtablestorescopiesoftheaffectedrowsduringDELETEandUPDATEstatements.DuringtheexecutionofaDELETEorUPDATEstatement,rowsaredeletedfromthetriggertableandtransferredtotheDELETEDtable.

TheINSERTEDtablestorescopiesoftheaffectedrowsduringINSERTandUPDATEstatements.Duringaninsertorupdatetransaction,newrowsareaddedtoboththeINSERTEDtableandthetriggertable.TherowsintheINSERTEDtablearecopiesofthenewrowsinthetriggertable.

Example:

WewillusetheCUSTOMERtableasanexample:

WewillcreateaTRIGGERthatwillcheckifthePhonenumberisvalidwhenweinsertorupdatedataintheCUSTOMERtable.Thevalidationcheckwillbeverysimple,i.e.,wewillcheckifthePhonenumberislessthan8digits(whichisnormallengthinNorway).IfthePhonenumberislessthan8digits,thefollowingmessage“PhoneNumberisnotvalid”bewritteninplaceofthewrongnumberinthePhonecolumn.

TheTRIGGERbecomessomethinglikethis:

IF EXISTS (SELECT name FROM sysobjects WHERE name = 'CheckPhoneNumber' AND type = 'TR') DROP TRIGGER CheckPhoneNumber GO CREATE TRIGGER CheckPhoneNumber ON CUSTOMER FOR UPDATE, INSERT AS DECLARE @CustomerId int, @Phone varchar(50), @Message varchar(50) set nocount on select @CustomerId = CustomerId from INSERTED select @Phone = Phone from INSERTED

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set @Message = 'Phone Number ' + @Phone + ' is not valid' if len(@Phone) < 8 --Check if Phone Number have less than 8 digits update CUSTOMER set Phone = @Message where CustomerId = @CustomerId set nocount off GO

WetesttheTRIGGERwiththefollowingINSERTINTOstatement:

INSERT INTO CUSTOMER (CustomerNumber, LastName, FirstName, AreaCode, Address, Phone) VALUES ('1003', 'Obama', 'Barak', 51, 'Nevada', '4444')

Theresultsbecome:

Asyoucansee,theTRIGGERworksasexpected.

WetrytoupdatethePhonenumbertoavalidnumber:

update CUSTOMER set Phone = '44444444' where CustomerNumber = '1003'

Theresultsbecome:

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13 CommunicationfromotherApplications

ADatabaseisastructuredwaytostorelotsofinformation.Theinformationisstoredindifferenttables.“Everything”todayisstoredindatabases.

Examples:

• Bank/Accountsystems • InformationinWebpagessuchasFacebook,Wikipedia,YouTube• …lotsofotherexamples

Thismeansweneedtobeabletocommunicatewiththedatabasefromotherapplicationsandprogramminglanguagesinordertoinsert,updateorretrievedatafromthedatabase.

13.1 ODBCODBC(OpenDatabaseConnectivity)isastandardizedinterface(API)foraccessingthedatabasefromaclient.Youcanusethisstandardtocommunicatewithdatabasesfromdifferentvendors,suchasOracle,SQLServer,etc.ThedesignersofODBCaimedtomakeitindependentofprogramminglanguages,databasesystems,andoperatingsystems.

WewillusetheODBCDataSourceAdministrator:



13.2 MicrosoftExcelMicrosoftExcelhastheabilitytoretrievedatafromdifferentdatasources,includingdifferentdatabasesystems.ItisverysimpletoretrievedatafromSQLServerintoExcelsinceExcelandSQLServerhasthesamevendor(Microsoft).

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14 ReferencesMyBlog:https://www.halvorsen.blog

MicrosoftofficialSQLServerWebsite-http://www.microsoft.com/sqlserver

SQLServerBooksOnline-http://msdn.microsoft.com/en-us/library/ms166020.aspx

SQLServerHelp

w3shools.com-http://www.w3schools.com/sql

Wikipedia–MicrosoftSQLServer-http://en.wikipedia.org/wiki/Microsoft_SQL_Server

Wikipedia-SQL-http://en.wikipedia.org/wiki/SQL

Wikipedia–TransactSQL-http://en.wikipedia.org/wiki/T-SQL

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