Dbms interview questions

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1. Interview questions

2. 1. What is Database ?
Adatabaseisacollectionofinformationthatisorganized.Sothatitcan
easilybeaccessed,managedandupdated.
DBMS INTERVIEW QUESTIONS WITH ANSWER

3. 2. What is DBMS ?
DBMSstandsforDatabaseManagementSystem.Itisacollectionof
programsthatenablesusertocreateandmaintainadatabase.
DBMS INTERVIEW QUESTIONS WITH ANSWER

4. 3. What is a Database system ?
ThedatabaseandDBMSsoftwaretogetheriscalledasDatabasesystem.
DBMS INTERVIEW QUESTIONS WITH ANSWER

5. 4. What are the advantages of DBMS ?
1.Redundancyiscontrolled.
2.Providingmultipleuserinterfaces.
3.Providingbackupandrecovery.
4.Unauthorizedaccessisrestricted.
5.Enforcingintegrityconstraints.
DBMS INTERVIEW QUESTIONS WITH ANSWER

6. 5. What is normalization ?
Itisaprocessofanalysingthegivenrelationschemasbasedontheir
FunctionalDependencies(FDs)andprimarykeytoachievetheproperties
1.Minimizingredundancy
2.Minimizinginsertion,deletionandupdateanomalies.
1. as
DBMS INTERVIEW QUESTIONS WITH ANSWER

7. 6. What is Data Model ?
Acollectionofconceptualtoolsfordescribingdata,datarelationshipsdata
semanticsandconstraints.
DBMS INTERVIEW QUESTIONS WITH ANSWER

8. 7. What is E-R model ?
Thisdatamodelisbasedonrealworldthatconsistsofbasicobjects
calledentitiesandoftherelationshipamongtheseobjects.Entitiesare
describedinadatabasebyaassetofattributes.
DBMS INTERVIEW QUESTIONS WITH ANSWER

9. 8. What is Object Oriented model ?
Thismodelisbasedoncollectionofobjects.Anobjectcontainsvalues
storedininstancevariableswithintheobject.Anobjectalsocontains
bodiesofcodethatoperateontheobject.Thesebodiesofcodearecalled
methods.Objectsthatcontainsametypesofvaluesandthesame
methodsaregroupedtogetherintoclasses.
DBMS INTERVIEW QUESTIONS WITH ANSWER

10. 9. What is an Entity ?
Anentityisathingorobjectofimportanceaboutwhichdatamustbe
captured.
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11. 10. What is DDL ?
DataDefinitionLanguage.
Adatabaseschemaisspecifiesbyasetofdefinitionsexpressedbya
speciallanguagecalledDDL.
DBMS INTERVIEW QUESTIONS WITH ANSWER

12. 11. What is DML ?
DataManipulationLanguage
Thislanguagethatenableusertoaccessormanipulatedataasorganisedby
appropriatedatamodel.
ProceduralDMLorLowlevel:DMLrequiresausertospecifywhatdataare
neededandhowtogerthosedata.
Non-ProceduralDMLorHighlevel:DMLrequiresausertospecifywhatdata
areneededwithoutspecifyinghowtogerthosedata.
DBMS INTERVIEW QUESTIONS WITH ANSWER

13. 12. What is DML Compiler ?
IttranslateDMLstatementsinaquerylanguageintolow-levelinstruction
thatthequeryevaluationenginecanunderstand.
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14. 13. What is Query evaluation engine ?
Itexecuteslow-levelinstructiongeneratedbycompiler.
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15. 14. What is Functional Dependency ?
FDisthestartingpointofnormalization.FDexistswhenarelation
betweentwoattributesallowsyoutouniquelydeterminethe
correspondingattribute’svalue.
DBMS INTERVIEW QUESTIONS WITH ANSWER

16. 15. What is 1 NF (Normal Form) ?
Thefirstnormalformor1NFisthefirstandthesimplesttypeof
normalizationthatcanbeimplementedinadatabase.Themainaimsof
1NFareto:
1.Eliminateduplicativecolumnsfromthesametable.
2.Createseparatetablesforeachgroupofrelateddataandidentify
eachrowwithauniquecolumn(theprimarykey).
DBMS INTERVIEW QUESTIONS WITH ANSWER

17. 16. What is Fully functional dependency ?
AfunctionaldependencyXYisfullfunctionaldependencyifremovalof
anyattributeAfromxmeansthatthedependencydoesnotholdany
more.
DBMS INTERVIEW QUESTIONS WITH ANSWER

18. 17. What is 2NF ?
ArelationschemaRisin2NFifitisin1NF.
Everynon-primeattributeAinRisfullyfunctionallydependentonprimary
key.
DBMS INTERVIEW QUESTIONS WITH ANSWER

19. 18. What is 3NF ?
Arelationisinthirdnormalformifitisinsecondnormalformandthere
arenofunctional(transitive)dependenciesbetweentwoormorenon-
primekeyattributes.
DBMS INTERVIEW QUESTIONS WITH ANSWER

20. 19. What is BCNF ?
Boyce-CoddNormalForm
AtableisinBCNFifandonlyifitisin3NFandeverydeterminantisa
candidatekey.
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21. 20. What is 4NF ?
FourthnormalformrequiresthatatablebeBCNFandcontainnomulti-
valueddependencies.
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22. 21. What is 5NF ?
Atableisin5NForProject-JoinNormalForm(PJNF)ifitisin4NFandit
cannothavealosslessdecompositionintoanynumberofsmallertables.
DBMS INTERVIEW QUESTIONS WITH ANSWER

23. 22. What is a query ?
AquerywithrespecttoDBMSrelatestousercommandsthatareusedto
interactwithadatabase.
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24. 23. What is meant by query optimization ?
Thephasethatidentifiesanefficientexecutionplanforevaluatingaquery
thathastheleastestimatedcostisreferredtoasqueryoptimization.
DBMS INTERVIEW QUESTIONS WITH ANSWER

25. 24. What is an attribute ?
Itisaparticularproperty,whichdescribestheentity.
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26. 25. What is RDBMS ?
RelationalDataBaseManagementSystem.
ItisDBMSthatmaintaindatarecordsandindicesintables.
DBMS INTERVIEW QUESTIONS WITH ANSWER

27. 26. What’s different between DBMS, RDBMS ?
DBMSprovidessystematicandorganizedwayofstoring,managingand
retrievingfromcollectionoflogicallyrelatedinformation.
RDBMSalsoprovideswhatDBMSprovidesbutabovethatitprovides
relationshipintegrity.
DBMS INTERVIEW QUESTIONS WITH ANSWER

28. 27. What is SQL ?
StructuredQueryLanguage.
SQLisanANSI(AmericanNationalStandardsInstitute)standard
computerlanguageforaccessingandmanipulatingdatabasesystems.
SQLstatementsareusedtoretrieveandupdatedatainadatabase.
DBMS INTERVIEW QUESTIONS WITH ANSWER

29. 28. What is Stored Procedure ?
AstoredprocedureisanamedgroupofSQLstatementthathavebeen
previouslycreatedandstoredintheserverdatabase.
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30. 29. What is a view ?
Aviewmaybeasubsetofthedatabaseoritmaycontainvirtualdatathat
isderivedfromthedatabasefilesbutisnotexplicitlystored.
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31. 30. What is Trigger ?
AtriggerisaSQLprocedurethatinitiatesanactionwhenanevent
(INSERT,DELETEorUPDATE)occurs.
DBMS INTERVIEW QUESTIONS WITH ANSWER

32. 31. What is Index ?
Anindexisaphysicalstructurecontainingpointerstothedata.
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33. 32. What is extension and intension ?
Extension:itisthenumberoftuplespresentinatableatanyinstance.
Thisistimedependent.
Intension:itisaconstantvaluethatgivesthename,structureoftableand
theconstraintslaidonit.
DBMS INTERVIEW QUESTIONS WITH ANSWER

34. 33. What do you mean by atomicity and
aggregation ?
Atomicity:thisstatesthatdatabasemodificationsmustfollowan“allor
nothing”rule.Eachtransactionissaidtobe“atomic”.Ifonepartofthe
transactionfail,theentiretransactionfails.
Aggregation:afeatureoftheentityrelationshipmodelthatallowsa
relationshipsettoparticipateinanotherrelationshipset.Thisisindicated
onanERdiagrambydrawingadashedboxaroundtheaggregation.
DBMS INTERVIEW QUESTIONS WITH ANSWER

35. 34. What is RDBMS KERNAL ?
TwoimportantpiecesofRDBMSarchitecturearethekernel,whichisthe
software,andthedatadictionary,whichconsistsofthesystem-leveldata
structureusedbythekerneltomanagethedatabase.
DBMS INTERVIEW QUESTIONS WITH ANSWER

36. 35. Name the sub-system of a RDBMS ?
I/O,Security,LanguageProcessing,ProcessControl,Storage
Management,LoggingandRecovery,DistributionControl,Transaction
Control,MemoryManagement,LockManagement.
DBMS INTERVIEW QUESTIONS WITH ANSWER

37. 36. How do you communicate with an RDBMS ?
YoucancommunicatewithanRDBMSusingStructuredQueryLanguage
(SQL)
DBMS INTERVIEW QUESTIONS WITH ANSWER

38. 37. Disadvantage of File Processing System.
•Dataredundancy&inconsistency.
•Difficultinaccessingdata.
•Dataisolation.
•Dataintegrity.
•Concurrentaccessisnotpossible.
•Securityproblems.
DBMS INTERVIEW QUESTIONS WITH ANSWER

39. 38. What is VDL ?
ViewDefinitionLanguage
Itspecifiesuserviewsandtheirmappingstotheconceptualschema.
DBMS INTERVIEW QUESTIONS WITH ANSWER

40. 39. What is SDL ?
StorageDefinitionLanguage.
Thislanguageistospecifytheinternalschema.Thislanguagemay
specifythemappingbetweentwoschemas.
DBMS INTERVIEW QUESTIONS WITH ANSWER

41. 40. Describe concurrency control ?
Concurrencycontrolistheprocessmanagingsimultaneousoperations
againstadatabasesothatdatabaseintegrityisnocompromised.There
aretwoapproachestoconcurrencycontrol.
Thepessimisticapproachinvolveslockingandtheoptimisticapproach
involvesversioning.
DBMS INTERVIEW QUESTIONS WITH ANSWER

42. 41. Describe the difference between
homogeneous and heterogeneous distributed
database.
HomogeneousdatabaseisonethatusesthesameDBMSateachnode.
HeterogeneousdatabaseisonethatmayhavedifferentDBMSateach
node.
DBMS INTERVIEW QUESTIONS WITH ANSWER

43. 42. What is a distributed database ?
Adistributeddatabaseisasinglelogicaldatabasethatisspreadacross
morethanonenodeorlocationsthatareallconnectedviasome
communicationlink.
DBMS INTERVIEW QUESTIONS WITH ANSWER

44. 43. Explain the difference between two and
three-tire architectures.
Three-tirearchitectureincludesaclientandtwoserverlayers.The
applicationcodeisstoredontheapplicationserverandthedatabaseis
storedonthedatabaseserver.
Two-tirearchitectureincludesaclientandoneserverlayer.Thedatabase
storedonthedatabaseserver.
DBMS INTERVIEW QUESTIONS WITH ANSWER

45. 44. Briefly describe the three types of SQL
commands.
Adatabaseisacollectionofinformationthatisorganized.Sothatitcan
easilybeaccessed,managedandupdated.
DBMS INTERVIEW QUESTIONS WITH ANSWER

46. 45. List some of the properties of a relation ?
Relationsinadatabasehaveauniquenameandnomultivaluedattributes
exist.
Eachrowsisuniqueandeachattributewitharelationhasauniquename.
Thesequenceofbothcolumnsandrowsisirrelevant.
DBMS INTERVIEW QUESTIONS WITH ANSWER

47. 46. Explain the differences between an intranet
and an extranet ?
AnIntranetdatabaseisaccessiblebyeveryonewhohasaccesstoa
website.
Anintranetdatabase limitsaccesstoonlypeoplewithinagiven
organization.
DBMS INTERVIEW QUESTIONS WITH ANSWER

48. 47. What is SQL Deadlock ?
Deadlockisauniquesituationinamultiusersystemthatcausestwoor
moreuserstowaitindefinitelyforalockedresource.
DBMS INTERVIEW QUESTIONS WITH ANSWER

49. 48. What is a Catalog?
Acatalogisatablethatcontainstheinformationsuchasstructureofeach
file,thetypeandstorageformatofeachdataitemandvariousconstraints
onthedata.
TheinformationstoredinthecatalogiscalledMetadata.
DBMS INTERVIEW QUESTIONS WITH ANSWER

50. 49. Describe the three level of abstraction.
PhysicalLevel:thelowestlevelofabstractiondescribeshowdataarestored.
LogicalLevel:thenexthigherlevelofabstraction,describeswhatdataare
storedindatabaseandwhatrelationshipamongthosedata.
ViewLevel:thehighestlevelofabstractiondescribesonlypartofentire
database.
DBMS INTERVIEW QUESTIONS WITH ANSWER

51. 50. How many types of relationship exist in
database design ?
1.One-to-one
2.One-to-many
3.Many-to-many
4.Many-to-one
DBMS INTERVIEW QUESTIONS WITH ANSWER

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