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Databases Test ...

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  • Question 1
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    A relation R(A, B, C) having the following tuples (2, 3, 4) (4, 1, 2) (5, 2, 2) (1, 3, 2). Which of the following functional dependency does not hold true from this relation?

  • Question 2
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    Which of the following is/are not a part of the ACID properties of database transactions?

  • Question 3
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    Consider the following relational schema for students(STU):

    id

    name

    age

    marks

    1

    PPP

    13

    56

    2

    QQQ

    14

    67

    3

    RRR

    13

    76

    4

    AAA

    15

    56

    5

    BBB

    14

    58

    6

    CCC

    16

    79

    7

    SSS

    16

    80

    8

    TTT

    13

    73

    9

    RRR

    14

    54

    10

    YYY

    15

    42

    The following query is made on the database.

    T1 → \({{\rm{\Pi }}_{id,name}}\left( {{\sigma _{age > 13 \wedge age < 16}}\left( {STU} \right)} \right)\)

    T2 → \({{\rm{\Pi }}_{id,name}}\left( {{\sigma _{marks > 55 \wedge marks < 66}}\left( {STU} \right)} \right)\)

    T → T2 - T1

    The total no. of rows in T is ______. 

  • Question 4
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    Let Account be a relation with attributes (customer_name, amount). Consider

    (i) {T |~Tϵ Account}

    (ii) {T | T ϵ Account}

    Which of the following statement is correct about this?

  • Question 5
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    Records are stored in some sorted order based on some search key and that search key is also sorted, is

  • Question 6
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    Let X (a, b, c, d) and Y (p, q, r, s) be two relations in which a is the foreign key of X that refers to the primary key of Y. Which of the following operation does not causes the referential integrity constraint violation?

  • Question 7
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    Consider 4 transactions T1, T2, T3, and T4 Transaction T1 has 5 transactions, T2 has 4 transactions,  T3 has 3 transactions and T4 has 2 transactions. What is the number of non-serial schedule?

  • Question 8
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    Which of the following statement is/are true?

    I. A transaction writes a data item after it is read by an uncommitted transaction leads to an irrecoverable error in a database system.

    II. Timestamp ordering protocol does not ensure freedom from deadlock

    III. In case of disk crash, Among the ACID property, the durability property fails to make changes successfully in the database

  • Question 9
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    Consider a schema R(X, Y, Z W) and functional dependencies X → Y and W → Z. Then the decomposition of R into T1(X, Y) and T2(Z, W) is

  • Question 10
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    Which of the following is/are true if a relation R has six attributes A, B, C, D, E, and F. The following functional dependencies hold AB → C, B → D, AD → F, C → D, D → E, E → F, F → D.

  • Question 11
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    Which of the following is true for the below given functional dependencies of the relation R(X, Y,Z,W) and S(X, Y, Z, W)?

    R: {X → Y, XY → Z, W → XZ, Z → W}

    S: {X → YZ, W → XY}

    I. R ⊇ S

    II. S ⊇ R

  • Question 12
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    Consider a relation R(ABC) with Functional dependency {AB → C, AC → B, BC → A}.Which of the following is/are TRUE about the normal form that the relation R is in?

  • Question 13
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    Database table name Tuition_Records is given below

    Students

    Teachers

    Fees

    Aniket

    Uday

    10000

    Barbie

    Rishi

    7000

    Chandresh

    Uday

    12000

    Dharma

    Rishi

    9000

     

    SELECT count(*) FROM ((SELECT students, Teachers FROM Tuition_Records) AS A NATURAL JOIN (SELECT Teachers, Fees FROM Tuition_Records))

    What is the output of the following SQL query?

  • Question 14
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    Consider the schema

    Sailors(sid, sname, rating, age) with the following data

    Sid

    Sname

    Rating

    age

    22

    Dustin

    7

    45

    29

    Borg

    1

    33

    31

    Pathy

    8

    55

    32

    Robert

    8

    25

    58

    Raghu

    10

    17

    64

    Herald

    7

    35

    71

    Vishnu

    10

    16

    74

    King

    9

    35

    85

    Archer

    3

    26

    84

    Bob

    3

    64

    96

    Flinch

    3

    17

    For the query

    SELECT S.rating, AVG(S.age) AS avgage FROM Sailors S

    Where S.age >= 18

    GROUP BY S.rating

    HAVING 1 < (SELECT COUNT(*) FROM Sailors S2 where S.rating = S2.rating)

    The number of rows returned is

  • Question 15
    2 / -0.33

    Consider the following schedule of transactions T1, T2, T3 and T4.

    T2: R(Y) T2: R(X); T3: R(X); T3: commit; T1:W(X); T2:W(Y); T2: R(z); T2: commit; T4: R(X); T4: R(Y); T1:W(Z); T1:commit; T4:commit.

    Which of the following is correct about this?

  • Question 16
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    Relation R has eight attributes ABCDEFGH. Fields of R contain only atomic values.

    F={CH→G, A→BC, B→CFH, E→A, F→EG} is a set of functional dependencies (FDs) so that F+ is

    exactly the set of FDs that hold for R.

    How many candidate keys does the relation R have?

  • Question 17
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    Consider a file based system in which total overhead for each entry in the file allocation table is 2 bytes in size. Given a 100 × 104 bytes of disk on which file system is stored. Block size of data is 102 bytes, then the maximum file size possible that can be stored on the disk is(in 104 bytes)?

  • Question 18
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    Consider the database that has the relation schema T (X, Y). An instance of the schema T is as given below:

    T1 ← ∏YX = A3 (T))

    T2 ← T ÷ T1

    X

    Y

    A1

    B1

    A1

    B2

    A2

    B1

    A2

    B2

    A1

    B3

    A3

    B1

    A3

    B2

    A2

    B1

    A4

    B1

    A3

    B3

    A4

    B2

     

    Find the number of rows in T2

  • Question 19
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    Which of the following is/are true?

  • Question 20
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    Consider the following transactions with data items X and Y initialized to zero:

    T1: read (x);

    Read (y);

    if x = 0 then y: = y + 1;

    Write (y);

    T2: read (y);

    write (x);

    If y = 0 then x: x + 1

    Write (x);

    The concurrent execution of T1­ and T­2 lead to

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