database management system - gnuopen.gnu.ac.kr/lecslides/2017-2-db/dblec01_intro... ·...

DatabaseManagementSystem

Lecture1

IntroductiontoRelationalDatabase

*SomematerialsadaptedfromR.Ramakrishnan,J.Gehrke

Today’sAgenda• CourseLayout

• IntroductiontoRelationalDatabase

• OverviewofSQLandMySQL

DatabaseManagementSystem 2

CourseLayout

AboutthisCourse• Instructor• SeongjinLee

• Email:insight@gnu.ac.kr

• Office:407-314

• OfficeHour:EveryThursday11:00-12:00orMakeappointment

• Class• Time:Thursday16:00-19:00

• Place:407-202

• Coursewebpage• http://203.255.57.228/MediaWiki/index.php?title=Database

• Textbook• DatabaseManagementSystem,3rd Ed.,Ramakrishnan&Gerhke,McGrawHill,2003

AboutthisCourse• Goal– Tocovermajortopicsindatabasemanagementsystem

• Evaluation• Attendance– 10%

• Quiz– 10%Shortquizzesatthebeginningofmostclasses

• Assignments– 10%

• Project– 20%

• Midterm– 30%

• Final- 30%

• Closedbookandnotes

• Requestforregradewithinoneweekuponreturn;describereasonsinwriting

• whatandwhythescoreisincorrectorunfair

• Thewrittenargumentmustbeself-contained

Topics• RelationalDatabase

• SQL

• LogicalDatabaseDesign• ConceptualModeling(Entity-RelationshipDiagram)

• Normalization

• DatabaseInternals• StorageandIndexing

• QueryOptimization

• PhysicalDatabaseDesign

• TransactionandRecovery

AboutthisCourse• ReadingAssignments– Duebeforefollowingclassperiod

• Upto6Homeworkassignments(maybeless)• Pleaseturninassignmentsbytheduedate(checkthewebsite)

• Attendance• Participationisimportantpartofthiscourse

• 3absenceswithoutpriorarrangementwillloweryourgradebyoneletter(eachsubsequent1absenceswillloweragradebyoneletter)

AboutthisCourse• AcademicHonesty• Assignments,quizzes,andexamsdoneindividually

• Nolying,cheating,copying

• Iffound,nogradeforthatparticularassessment

• Suspiciousworkwillbequestionedthoroughly

AboutthisCourse• Noclasseson추석 thatisonOctober5th

• MidtermandFinal• Closebookandnotes

• MidtermonOct.19th (inclass)

• FinalonDec.14th (inclass)

• Quizzes• Togivefeedbackonyourunderstandingofmaterialaswellashelpwithmaterial

• atthebeginningofmostoftheclasses

• Basedonthepreviousclassmaterial

IntroductiontoRelationalDatabase

WhatIsaDBMS?• Averylarge,integratedcollectionofdata.

• Modelsreal-worldenterprise.• Entities (e.g.,students,courses)

• Relationships (e.g.,MadonnaistakingCS564)

• ADatabaseManagementSystem(DBMS)isasoftwarepackagedesignedtostoreandmanagedatabases.

Filesvs.DBMS• Applicationmuststagelargedatasetsbetweenmainmemoryandsecondarystorage(e.g.,buffering,page-orientedaccess,32-bitaddressing,etc.)

• Specialcodefordifferentqueries

• Mustprotectdatafrominconsistencyduetomultipleconcurrentusers

• Crashrecovery

• Securityandaccesscontrol

WhyUseaDBMS?• Dataindependenceandefficientaccess.

• Reducedapplicationdevelopmenttime.

• Dataintegrityandsecurity.

• Uniformdataadministration.

• Concurrentaccess,recoveryfromcrashes.

WhyStudyDatabases??(1/2)• Itiscriticaltogovernment,business,science,etc.

• Manytechcompaniesarebuildondatamanagement(Google,Amazon,Facebook,Netflix,etc.)• ortheyofferdatabaseproducts(IBM,Oracle,Microsoft,etc.)

• Shiftfromcomputation toinformation• atthe“lowend”:scrambletowebspace(amess!)

• atthe“highend”:scientificapplications

• Datasetsincreasingindiversityandvolume.• Digitallibraries,interactivevideo,HumanGenomeproject,EOSproject

• ...needforDBMSexploding

WhyStudyDatabases??(2/2)• Itspansmajorareasofcomputerengineering• Operatingsystems(file,memory,processmanagement)

• Theory(languages,algorithms,complexity)

• ArtificialIntelligence(knowledge-basedsystems,logic,search)

• SoftwareEngineering(applicationdevelopment)

• Datastructures(trees,hashtables)

• Datamaybeverylarge• Amazon>42TB

• Youtube >45TB

• AT&%>323TB

• NationalEnergyResearchScientificComputingCenter>2.8Petabytes

1TB=1,000,000,000,000Bytes1PB=1,000,000,000,000,000Bytes

DataModels• Adatamodel isacollectionofconceptsfordescribingdata.

• Aschema isadescriptionofaparticularcollectionofdata,usingtheagivendatamodel.

• Therelationalmodelofdataisthemostwidelyusedmodeltoday.

• Mainconcept:relation,basicallyatablewithrowsandcolumns.

• Everyrelationhasaschema,whichdescribesthecolumns,orfields.

LevelsofAbstraction• Manyviews,singleconceptual(logical)schema andphysicalschema.• Viewsdescribehowusersseethedata.

• Conceptualschemadefineslogicalstructure

• Physicalschemadescribesthefilesandindexesused.

☛ Schemas are defined using DDL; data is modified/queried using DML.

Physical Schema

Conceptual Schema

View 1 View 2 View 3

Example:UniversityDatabase• Conceptualschema:

Students(sid:string,name:string,login:string,age:integer,gpa:real)

Courses(cid:string,cname:string,credits:integer)

Enrolled(sid:string,cid:string,grade:string)

• Physicalschema:• Relationsstoredasunorderedfiles.

• IndexonfirstcolumnofStudents.

• ExternalSchema(View):Course_info(cid:string,enrollment:integer)

DataIndependence*• Applicationsinsulatedfromhowdataisstructuredandstored.

• Logicaldataindependence:Protectionfromchangesinlogicalstructureofdata.

• Physicaldataindependence:Protectionfromchangesinphysicalstructureofdata.

☛ One of the most important benefits of using a DBMS!

ConcurrencyControl• ConcurrentexecutionofuserprogramsisessentialforgoodDBMSperformance.• Becausediskaccessesarefrequent,andrelativelyslow,itisimportanttokeeptheCPUhummingbyworkingonseveraluserprogramsconcurrently.

• Interleavingactionsofdifferentuserprogramscanleadtoinconsistency:e.g.,checkisclearedwhileaccountbalanceisbeingcomputed.

• DBMSensuressuchproblemsdon’tarise:userscanpretendtheyareusingasingle-usersystem.

Transaction:AnExecutionofaDBProgram• Keyconceptistransaction,whichisanatomicsequenceofdatabaseactions(reads/writes).

• Eachtransaction,executedcompletely,mustleavetheDBinaconsistentstate ifDBisconsistentwhenthetransactionbegins.• Userscanspecifysomesimpleintegrityconstraintsonthedata,andtheDBMSwillenforcetheseconstraints.

• Beyondthis,theDBMSdoesnotreallyunderstandthesemantics ofthedata.(e.g.,itdoesnotunderstandhowtheinterestonabankaccountiscomputed).

• Thus,ensuringthatatransaction(runalone)preservesconsistencyisultimatelytheuser’sresponsibility!

SchedulingConcurrentTransactions• DBMSensuresthatexecutionof{T1,...,Tn}isequivalenttosomeserialexecutionT1’...Tn’.• Beforereading/writinganobject,atransactionrequestsalockontheobject,andwaitstilltheDBMSgivesitthelock.Alllocksarereleasedattheendofthetransaction.(Strict2PLlockingprotocol.)

• Idea:IfanactionofTi(say,writingX)affectsTj(whichperhapsreadsX),oneofthem,sayTi,willobtainthelockonXfirstandTjisforcedtowaituntilTicompletes;thiseffectivelyordersthetransactions.

• WhatifTjalreadyhasalockonYandTilaterrequestsalockonY?(Deadlock!)TiorTjisaborted andrestarted!

EnsuringAtomicity• DBMSensuresatomicity (all-or-nothingproperty)evenifsystemcrashesinthemiddleofaXact.

• Idea:Keepalog (history)ofallactionscarriedoutbytheDBMSwhileexecutingasetofXacts:• Before achangeismadetothedatabase,thecorrespondinglogentryisforcedtoasafelocation.(WALprotocol;OSsupportforthisisofteninadequate.)

• Afteracrash,theeffectsofpartiallyexecutedtransactionsareundone usingthelog.(ThankstoWAL,iflogentrywasn’tsavedbeforethecrash,correspondingchangewasnotappliedtodatabase!)

TheLog• Thefollowingactionsarerecordedinthelog:• Tiwritesanobject:Theoldvalueandthenewvalue.

• Logrecordmustgotodiskbefore thechangedpage!

• Ticommits/aborts:Alogrecordindicatingthisaction.

• LogrecordschainedtogetherbyXactid,soit’seasytoundoaspecificXact(e.g.,toresolveadeadlock).

• Logisoftenduplexedandarchivedon“stable”storage.

• Alllogrelatedactivities(andinfact,allCCrelatedactivitiessuchaslock/unlock,dealingwithdeadlocksetc.)arehandledtransparentlybytheDBMS.

Databasesmakethesefolkshappy...• EndusersandDBMSvendors

• DBapplicationprogrammers• E.g.,smartwebmasters

• Databaseadministrator(DBA)• Designslogical/physicalschemas

• Handlessecurityandauthorization

• Dataavailability,crashrecovery

• Databasetuningasneedsevolve

Must understand how a DBMS works!

StructureofaDBMS(Fig.1.3,p.20)• AtypicalDBMShasalayeredarchitecture.

• Thisisoneofseveralpossiblearchitectures;eachsystemhasitsownvariations.

SummaryofChapter1• DBMSusedtomaintain,querylargedatasets.

• Benefitsincluderecoveryfromsystemcrashes,concurrentaccess,quickapplicationdevelopment,dataintegrityandsecurity.

• Levelsofabstractiongivedataindependence.

• ADBMStypicallyhasalayeredarchitecture.

• DBAsholdresponsiblejobsandarewell-paid!J

• DBMSR&Disoneofthebroadest,mostexcitingareasinCS.

TheRelationalModelChapter3to3.3

Theterminology

RelationalDatabase• Assumethefollowingtable(A.K.ARelation)hasbeendefinedtokeeptrackofstudents

Number Name Balance Type

7003001 JaneSmith 1,000,000 Savings

7003003 AlfredHitchcock 4,400,200 Savings

7003005 TakumiFujiwara 2,230,000 Checking

7003007 Brian Mills 1,200,000 Savings

7003009 JasonBourn 3,025,000 Checking

Account

Terminology• Thenameofthetable(relation):Students

Account

Terminology• Thenameoftheattributes(columns):SID,NAME,Department,GPA)

Account

Terminology• Schemaofthetable• Definitionandstructureoftherelation(includestypesandconstraints)

Account

Constraints• Foreveryattributeofeveryrelation,theschemaspecifiesallowablevalues

• Theallowablevaluesforanattributeiscalledthe“domain”oftheattribute

Account(Number:integer,name:string,Balance:currency,type:string)

Terminology• Eachentryintherelationiscalled“row”,“tuple”,or“record”

• Instanceoftheschemaisthecurrentsetofrows

instancerows

Account

Terminology• “Degree”ofrelationisthenumberofattributes

• “Cardinality”ofrelationisthenumberofrowsinthecurrentinstance

Degreeofthisrelationis4(therearefourattributes,SID,Name,Department,GPA)

Cardinality

Cardinalityofthisinstanceis6(Thereare6rows)

Account

Terminology• EachTablehaskey

• Thevalueofthekeymustbeunique

• Whatisthekeyfortheeachrelations

Account

Accnt TxID Date Amount

7003007 1 16-Aug-2017 200

7003001 2 19-Aug-2017 400

7003003 3 26-Aug-2017 100

7003009 4 26-Aug-2017 840

Deposit

Number ChkNo Date Amount

7003003 123 29-Aug-2017 840

7003003 124 30-Aug-2017 320

Terminology• Keyconsistsofoneormoreattributes

• Generallyunderlinethekeyattributes

Account

7003007 1 16-Aug-2017 200

7003001 2 19-Aug-2017 400

7003003 3 26-Aug-2017 100

7003009 4 26-Aug-2017 840

Deposit

7003003 123 29-Aug-2017 840

7003003 124 30-Aug-2017 320

Constraints• SeetheDepositRelations

• Howcanwepreventitfromhappening?• UseforeignKey

• Deposit.Accnt isaforeignkey thatreferencesAccount.Number

• Calledenforcingreferentialintegrity

Account

7003007 1 16-Aug-2017 200

7003001 2 19-Aug-2017 400

7003003 3 26-Aug-2017 100

7003009 4 26-Aug-2017 840

7003011 5 27-Aug-2017 2100

Deposit

Terminology• Foreignkeysmayormaynotbepartofthekeyfortherelation

• Deposit.AccntisnotpartofthekeyforDeposit

• Check.Numberispartofthekeyforcheck

Account

7003007 1 16-Aug-2017 200

7003001 2 19-Aug-2017 400

7003003 3 26-Aug-2017 100

7003009 4 26-Aug-2017 840

Deposit

7003003 123 29-Aug-2017 840

7003003 124 30-Aug-2017 320

MoreonSchema• Selectthetables,withanameforeachtable• adatabaseschemamayhavemultipletables

• Eachtablehasitsownschema

• Selectattributesforeachtableandgivethedomainforeachattribute

• Specifythekey(s)foreachtable• therecanbemorethan1keyforatable

• Specifyallappropriateforeignkeys

Exercise• Createarelationwithonekey

• Createarelationwithsomeforeignkeysbasedonthefirstrelation

StructuredQueryLanguage(SQL)Chapter3.4

StructuredQueryLanguage(SQL)• ItisthelanguageusedtotalktoDBMS,andservesmanypurposes

• Todefineaboveschema

Account(Number:integer,name:character,Balance:currency,type:character)

CREATETABLEAccount(NumberintegerNOTNULL,Namecharacter,Balancecurrency,Typecharacter,PRIMARYKEY(Number)

)DatabaseManagementSystem 43

StructuredQueryLanguage(SQL)• Toquerythedatabase

• Toinsertrowsintoatable:

INSERTINTOAccountVALUES(106,“LucyLou”,124000,“savings”);

SELECT*FROMAccountWHEREType=“checking”;

QueryExample1• Showtheaccountthatmadedepositmorethan500

• SQLqueriesreturnnewtablesrepresentingtheanswertothequery

7003007 1 16-Aug-2017 200

7003001 2 19-Aug-2017 400

7003003 3 26-Aug-2017 100

7003009 4 26-Aug-2017 840

Deposit

SELECTAccnt,AmountFROMDepositWHEREAmount>500;

7003007 1 16-Aug-2017 200

7003001 2 19-Aug-2017 400

7003003 3 26-Aug-2017 100

7003009 4 26-Aug-2017 840

QueryExample1cont’d• SQLqueriesreturnnewtablesrepresentingtheanswertothequery

Accnt Amount

7003009 840

Deposit

QueryExample2• Showthetransactionnumber3

• EachrowischeckedtoseeifWHEREclauseevaluatestotrue

• “*”Returneverycolumn

7003007 1 16-Aug-2017 200

7003001 2 19-Aug-2017 400

7003003 3 26-Aug-2017 100

7003009 4 26-Aug-2017 840

Deposit

SELECT*FROMDepositWHERETxID=3;

7003003 3 26-Aug-2017 100

Exercises• Writethequerytoshowallinformationfromaccountswithcheckingtype

• Howaboutallaccountswithsavingstype

• Ifyouwanttoknowtheowneroftheaccountswithcheckingtype,howwouldyouwritethequery

QueryExample3

• Whatwouldbetheoutcomeofthequery?

Account

SELECT*FROMAccountWHEREType=“checking”

ANDType=“savings”;

Answerisempty

EmptyQueryResults

• Itisnoterror,andcanbeinformativeinasense

• Becauseofthedomainofthetypeattributewillnevergiveanyresulttothequery

SELECT*FROMAccountWHEREType=“checking”

ANDType=“savings”;

Account

EvaluatingtheSQLQuery1. FROMclausetellstheinputtables

2. Whereclauseisevaluatedforallcombinationsofrowsfromtheinputtables

3. SELECTclausedecideswhichattributesremainsinthequeryresult

SELECTAccnt,AmountFROMDepositWHEREAmount>500;

Queriesovertwotables:a”Join”

• WhichrowsfromwhichtablesareevaluatedintheWHEREclause?

• “A”isacorrelationnameforAccount

• “D”isacorrelationnameforDeposit• Correlationnameactsasalocalvariable

• Holdsonerowfromthecorrespondingtable

• Tablenamecanalsobeusedasacorrelationname,butitislonger

SELECTA.Name,A.BalanceFROMAccountA,DepositDWHEREA.Number=D.Account AND

A.Balance>2,200,000;

QueryExample4

• Checkeverycombinationofonerowfromeachtable

Account

7003007 1 16-Aug-2017 200

7003001 2 19-Aug-2017 400

7003003 3 26-Aug-2017 100

7003009 4 26-Aug-2017 840

Deposit

SELECTA.Name,A.BalanceFROMAccountA,DepositDWHEREA.Number=D.Account ANDA.Balance>2,200,000;

QueryExample4

Account

7003007 1 16-Aug-2017 200

7003001 2 19-Aug-2017 400

7003003 3 26-Aug-2017 100

7003009 4 26-Aug-2017 840

Deposit

EvaluateeachrowIfnottrue,Throw!

Number Name Balance Type Accnt TxID Date AmountIntermediateQueryResultTable

QueryExample4

Account

7003007 1 16-Aug-2017 200

7003001 2 19-Aug-2017 400

7003003 3 26-Aug-2017 100

7003009 4 26-Aug-2017 840

Deposit

EvaluateeachrowIfnottrue,Throw!

Number Name Balance Type Accnt TxID Date AmountIntermediateQueryResultTable

QueryExample4

Account

7003007 1 16-Aug-2017 200

7003001 2 19-Aug-2017 400

7003003 3 26-Aug-2017 100

7003009 4 26-Aug-2017 840

Deposit

EvaluateeachrowIftrue,Take!

Number Name Balance Type Accnt TxID Date Amount

7003003 AlfredHitchcock 4,400,200 Savings 7003003 3 26-Aug-2017 100

IntermediateQueryResultTable

QueryExample4

Account

7003007 1 16-Aug-2017 200

7003001 2 19-Aug-2017 400

7003003 3 26-Aug-2017 100

7003009 4 26-Aug-2017 840

Deposit

7003009 JasonBourn 3,025,000 Checking 7003009 4 26-Aug-2017 840

QueryExample4

Account

7003007 1 16-Aug-2017 200

7003001 2 19-Aug-2017 400

7003003 3 26-Aug-2017 100

7003009 4 26-Aug-2017 840

Deposit

Name Balance

AlfredHitchcock 4,400,200

JasonBourn 3,025,000

FinalQueryResultTable

UsefulKeyword:DISTINCT• Suppose

• DISTINCTremovesduplicaterows

SELECTDISTINCTA.Name,A.BalanceFROMAccountA,DepositDWHEREA.Number=D.Account ANDA.Balance>2,200,000;

Name Balance

FinalQueryResultTableName Balance

FinalQueryResultTable

w/oDISTINCT w/DISTINCT

Exercise

• Howmanyrowswillbeinthequeryresult?

• Howmaycolumnswillbeinthequeryresult?

Account

7003007 1 16-Aug-2017 200

7003001 2 19-Aug-2017 400

7003003 3 26-Aug-2017 100

7003009 4 26-Aug-2017 840

Deposit

SELECTA.Number,A.Name,D.Date,D.AmountFROMAccountA,DepositDWHEREA.Number=D.Account ANDD.Amount>100;

NotesonQueries• Aqueryisexpressedagainsttheschema

• But,thequeryisexecutedagainsttheinstance,thatisagainstthedata

• Theresultofaqueryisalwaysatable• resultingtabledonotalwayshaveaname

• Attributesdeducedfrominputtables

• resultmaynothaveanyrows

NotesonQueries• SelfJoins– Here,A1andA2refertocopiesofthesameinstance

SELECTA1.Number,A2.NumberFROMAccountA1,AccountA2WHEREA1.Balance=A2.BalanceAND

A1.Number>A2.Number;

NotesonQueries

• Namingattributesandqueryresult

• MyTablecanbeusedasatableinsubsequentqueries

• Remembertodeletethetemporarytables!

Account

Owner Amount

TakumiFujiwara 2,230,000

MyTable

SELECTNameAsOwner,BalanceasAmountINTOMyTableFROMAccountWHEREType=“Checking”;

TypicalDatabaseLifecycle

DesignDataModel

[ERDiagram]

CreateSchema[RelationalTables]

RemoveRedundancy

[Normalization]

DetermineIndexes

[PhysicalDesign]

ManageTables[SQL]

ImplementInterface

[Application]

[ch.2] [ch.3] [ch.21]

[ch.6,7] [ch.4,5] [ch.22]

ForNextWeek• Review– Quizonthematerial• Ch.1

• Ch.3to3.3

• Ch.5to5.2

• Readingassignments• Ch.4to4.2

• Ch.5.5

• Besureyouunderstand• thebasicterminology

• BasicSQLQueries(SELECT,FROM,WHERE)

database management system - gnuopen.gnu.ac.kr/lecslides/2017-2-db/dblec01_intro... ·...

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