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Database interview questions for beginner

Discussion in 'Database' started by shabbir, May 25, 2005.

  1. shabbir

    shabbir Administrator Staff Member

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    1. Explain the difference between a database administrator and a data administrator.

    Database Administrator :- A person (or group of people) responsible for the maintenance and performance of a database and responsible for the planning, implementation, configuration, and administration of relational database management systems.

    Data Administrator :- The individual or organization responsible for the specification, acquisition, and maintenance of data management software and the design, validation, and security of files or databases. The DA is in charge of the data dictionary and data model.

    2. Explain the difference between an explicit and an implicit lock.

    Explicit Lock :- Lock is explicitly requested for a record or table.
    Implicit Lock :- Lock is implied but is not acquired

    3. What is lock granularity?

    There are many locks available for the database system to have like
    Intent Shared, Shared, Intent exclusive, exclusive and Shared Intent exclusive.
    Locking granularity refers to the size and hence the number of locks used to ensure the consistency of a database during multiple concurrent updates.

    4. In general, how should the boundaries of a transaction be defined?

    A transaction ensures that one or more operations execute as an atomic unit of work. If one of the operations within a transaction fails, then all of them are rolled-back so that the application is returned to its prior state. The boundaries that define a group of operations done within a single transaction.

    5. Explain the meaning of the expression ACID transaction.

    ACID means Atomic, Consistency, Isolation, Durability, so when any transaction happen it should be Atomic that is it should either be complete or fully incomplete. There should not be anything like Semi complete. The Database State should remain consistent after the completion of the transaction. If there are more than one Transaction then the transaction should be scheduled in such a fashion that they remain in Isolation of one another.Durability means that Once a transaction commits, its effects will persist even if there are system failures.

    6. Explain the necessity of defining processing rights and responsibilities. How are such responsibilities enforced?

    One of the reason to define rights is the security in the database system. If any user is allowed to define the data or alter the data then the database would just be of no use and so processing rights and responsibilities are clearly defined in any database system. The resposibilities are enforced using the table space provided by the database system.

    7. Describe the advantages and disadvantages of DBMS-provided and application-provided security.

    DBMS provided security :- Any database system requires you to login and then process the data depending on the rights given by the DBA to the user who has logged in. The advatage of such a system is securing the data and providing the user and the DBA the secured platform. Any user who logs in cannot do whatever he want but his role can be defined very easily. There is no major disadvantage about the DBMS provided security apart from overhead of storing the rights and priviledges about the users.

    Application-provided security :- It is much similar to the DBMS provided security but the only difference is that its the duty of the programmer creating the application to provide all the seurities so that the data is not mishandled.

    8. Explain how a database could be recovered via reprocessing. Why is this generally not feasible?

    If we reprocess the transaction then the database can be made to come to a state where the database is consistent and so reprocessing the log can recover the database. Reprocessing is not very feasible for a very simple reason that its very costly from time point of view and requires lots of rework and many transaction are even rollback giving more and more rework.

    9. Define rollback and roll forward.

    Rollback :- Undoing the changes made by a transaction before it commits or to cancel any changes to a database made during the current transaction
    RollForward :- Re-doing the changes made by a transaction after it commits or to overwrite the chnaged calue again to ensure consistency

    10. Why is it important to write to the log before changing the database values?

    The most important objective to write the log before the database is changed is if there is any need to rollback or rollforward any transaction then if the log are not present then the rollback rollforward cannot be done accurately.
     
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  2. rollings

    rollings New Member

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    Thanks shabbir. , just got What I wanted
     
  3. shabbir

    shabbir Administrator Staff Member

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    My pleasure.
     
  4. clocking

    clocking New Member

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    Hi shabbir, I hesitate to suggest you this problem.
    Can You support me to designing a database for images of data?
     
  5. stylishkishore

    stylishkishore New Member

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    nice ...very nice.
     
  6. naimish

    naimish New Member

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    Wouldn't know we can also post like this :D Thanks.
     
  7. Daisy

    Daisy New Member

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    it was really benefit for me. because i am prepairing for competitative exams. thanks a lot shabbir
     
  8. sameer_havakajoka

    sameer_havakajoka New Member

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    can we plz hav sum sql server questions and answers too?
     
  9. jerryvn01

    jerryvn01 New Member

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    Hi,

    Thanks very much for this comment. It help me to think about my ideals.

    Tks again and pls keep posting.
     
  10. ksrao

    ksrao New Member

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    Hi,

    This is really a useful set of oracle sql interview questions for beginner.
    I found some more good questions for free at wiziq .


    Kolla Sanjeeva Rao.
    OCP
    Oracle.
     
  11. Malik-Qasim

    Malik-Qasim New Member

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  12. GoodCoder

    GoodCoder New Member

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    Hi,

    It is really helpful. :)

    Thanks.
     
  13. vinaykumar4670

    vinaykumar4670 Banned

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    thanks for support me.
     
  14. patricholier

    patricholier New Member

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    Hi

    This topic help me a lot in developing my project. I will contribute more when I finished it.
     
  15. Eldridge13

    Eldridge13 New Member

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    Hi, shabbir
    This topic is very useful for me. It makes me think about my ideals.
     
  16. shabbir

    shabbir Administrator Staff Member

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    Great to see that.
     
  17. hamburg113

    hamburg113 New Member

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    Hi

    I found that a member asked same question in this forum some months ago.

    Pls use search box to find this questions with comments
     
  18. shabbir

    shabbir Administrator Staff Member

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    Why don't you yourself use the same search box and find that user's query and reply to it instead of adding your reply here.
     
  19. angel46

    angel46 New Member

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    i have a question..
    Q)find the no. of superkeys that can be formed in the relation R(a1,a1,..,an) having a1 and a2 as keys?
     
  20. jhonackerman

    jhonackerman Banned

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    Hey thanks for the answering these interview questions,i really appreciate it.
     

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