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Technical Interview Questions and Answers :: DBMS

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    What is Normalization? Write different NFs?
    Answer:

    It is a process of analyzing the given relation schemas based on their Functional Dependencies (FDs) and primary key to achieve the properties
    > Minimizing redundancy
    > Minimizing insertion, deletion and update anomalies.

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    42 / 143

    What is Functional Dependency?
    Answer:

    A Functional dependency is denoted by X->Y between two sets of attributes X and Y that are subsets of R specifies a constraint on the possible tuple that can form a relation state r of R. The constraint is for any two tuples t1 and t2 in r if t1[X] = t2[X] then they have t1[Y] = t2[Y]. This means the value of X component of a tuple uniquely determines the value of component Y.

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    43 / 143

    When is a functional dependency F said to be minimal?
    Answer:

    > Every dependency in F has a single attribute for its right-hand side.
    > We cannot replace any dependency X A in F-> with a dependency Y A where Y-> is a proper subset of X and still have a set of dependency that is equivalent to F.
    > We cannot remove any dependency from F and still have set of dependency that is equivalent to F.

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    44 / 143

    What is Multivalued dependency?
    Answer:

    Multivalued dependency denoted by X -> Y specified on relation schema R, where X and Y are both subsets of R, specifies the following constraint on any relation r of R: if two tuples t1 and t2 exist in r such that t1[X] = t2[X] then t3 and t4 should also exist in r with the following properties
    > t3[x] = t4[X] = t1[X] = t2[X]
    > t3[Y] = t1[Y] and t4[Y] = t2[Y]
    > t3[Z] = t2[Z] and t4[Z] = t1[Z]
    where [Z = (R-(X U Y)) ]

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    45 / 143

    What is Lossless join property?
    Answer:

    It guarantees that the spurious tuple generation does not occur with respect to relation schemas after decomposition.

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    46 / 143

    What is 1 NF (Normal Form)?
    Answer:

    The domain of an attribute must include only atomic (simple, indivisible) values.

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    47 / 143

    What is Fully Functional dependency?
    Answer:

    It is based on the concept of full functional dependency. A functional dependency X -> Y is full functional dependency if removal of any attribute A from X means that the dependency does not hold any more.

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    Answer:

    A relation schema R is in 2NF if it is in 1NF and every non-prime attribute A in R is fully functionally dependent on primary key.

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    Answer:

    A relation schema R is in 3NF if it is in 2NF and for every FD X -> A either of the following is true
    > X is a Super-key of R.
    > A is a prime attribute of R.
    In other words, if every non prime attribute is non-transitively dependent on primary key.

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    50 / 143

    What is BCNF (Boyce-Codd Normal Form)?
    Answer:

    A relation schema R is in BCNF if it is in 3NF and satisfies an additional constraint that for every FD X -> A, X must be a candidate key.

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Database Management System(DBMS) is an important subject for Freshers and Experienced candidates, Who are looking to grab a job as a Database Developer or Administrator. Practice the frequently Asked DBMS Interview Questions Answers, Interview Questions on DBMS asked at Freshers and Experienced level. Most of the listed questions here have been previously asked during the technical rounds in IT companies. You can test your SQL database knowledge by solving these questions and compare your chances of getting the job with a top IT company.

Go through the basics of Database Management System before the interview process. Here, listed DBMS interview questions are Frequently asked during an Interview with different companies like Wipro, Accenture, TCS, Oracle, CTS, Adobe, TechM.

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