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In which of the topology, each device has a dedicated point-to-point l...

  • Q. In which of the topology, each device has a dedicated point-to-point link to a central controller?
  • filter_dramaExplanation
    Answer is : D

    Concept:

    A multipoint connection is one in which more than two specific devices share a single link

    A point-to-point connection provides a dedicated link between two devices

    In mesh, star and ring topologies are point-to-point connection

    Mesh topology

    In a mesh topology, every device has a dedicated point-to-point link to every other device

    Bus Topology

    In Bus Topology, one long cable acts as a backbone to link all the devices in a network

    Ring topology

    In a ring topology, each device has a dedicated point-to-point connection with only the two devices on either side of it; Each device is connected to its corresponding repeater

    Star topology

    In a star topology, each device needs only one link and one I/O port to connect it to any number of other devices

    Each device has a dedicated point-to-point link to a central controller known as a hub or switch

    Therefore star topology is the correct answer

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Similar Questions

  • 1.

    consider the schedule S given below.

    \(S:\;{R_1}\left( X \right),\;{W_2}\left( X \right),\;{W_1}\left( X \right)\),

    Which of the following statement is correct?
  • filter_dramaExplanation
    Answer is : C

    It is not a conflict serializable as there exists a cycle in the dependency graph given below

    it is not view-serializable.

    The reason is there may be 2 schedules possible:

    1. \({T_{1\;}} \to {T_2}\)

    2. \({T_2} \to {T_1}\)

    in case 1 final write of x is done by T2, but in the given schedule S, the final write of x is done by T1. so it violates the condition of view serializability.

    in case 2 initial read of T1 is updated value by T2 but in the original schedule, it is directly reading the database, again the condition of view serialization failed.

    So, C is correct answer.

  • 2.

    Consider the following SQL query:

    PROJ(Pnum, Dnum)

    DEPT(Dnumber, Mgr_Ssn)
    EMP(fname, lname, Ssn)

    Works_ON(Pno, ESSn)

    (SELECT DISTINCT Pnum

    FROM PROJ, DEPT, EMP WHERE Dnum = Dnumber

    AND Mgr_ssn = Ssn AND Lname=’XXXX’)

    UNION

    (SELECT DISTINCT Pnum FROM PROJ, WORKS_ON, EMP WHERE Pnum=Pno AND ESSn=Ssn

    AND Lname=’XXXX’)

  • filter_dramaExplanation
    Answer is : A

    The main Query has two Subquery 

    Subquery 1

    SELECT DISTINCT Pnum FROM PROJ, DEPT, EMP WHERE Dnum=Dnumber AND Mgr_ssn=Ssn AND Lname=’XXXX’)

    This query result as unique Pnum which is project number from the table PROJ, DEPT, EMP 

    where three Conditions will follow 

    Dnum=Dnumber

    Mgr_ssn=Ssn 

    Lname=’XXXX’

    As AND operator is used it will be treated as mandatory to follow all the conditions

    So here we will get the project number for those Whose last name is "XXXX"  and Mgr_ssn is the same as Ssn and Dnum is the same as Dnumber  (Assume Mgr_SSn is for Manager (who is also an employee))

    Subquery 2

    (SELECT DISTINCT Pnum FROM PROJ, WORKS_ON, EMP WHERE Pnum=Pno AND ESSn=Ssn

    AND Lname=’XXXX’)

    This query result as unique Pnum which is project number from the table PROJ, WORKS_ON, EMP

    where again three Condition will follow 

    Pnum=Pno 

    ESSn=Ssn

    Lname=’XXXX’

    Again AND operator is used it will be treated as mandatory to follow all the conditions

    So here we will get the project number for those Whose last name is "XXXX"  and ESSn_ssn is the same as Ssn and Pnum is the same as Pno. (Assume ESSn is for the worker  (who is also an employee))

    and At the End, The Union of both Subquery displayed as a result

    All project numbers for projects that involve an employee with the last name ‘XXXX’, either as a worker or as a manager  

    Therefore option 1 is correct

  • 3. Let R(A, B, C, D) be a relation schema and F = {A  BC, AB → D, B → C} be the set of functional dependencies defined over R. Which of the following represents the closure of the attribute set {B}?
  • filter_dramaExplanation
    Answer is : B

    Concept:- 

    Functional Dependencies:- Functional dependencies are the result of the interrelationship between attributes of any relation. Suppose in relation R, X and Y are two the two subsets of the set of attributes, Y is said to be functionally dependent on X if a given value of X uniquely determines the value of Y.

    It is denoted by X → Y. It means Y depends upon X or X holds Y.

    Here X is known as a determinant of functional dependency.

    Explanation:-

    Here, given R( A, B, C, D ) be a relation schema

    and, F = {A → BC, AB → D, B → C} be the set of functional dependencies defined over R.

    Closure of attributes {B}:-

    B= { B }

         = { B , C } ( using B →C )

    We can not determine any other attributes B and C  contained in the result set.

    Thus, 

    B+ = { B , C }

  • 4. Truncating tables shall ________.
  • filter_dramaExplanation
    Answer is : A

    The correct answer is option 1.

    Concept:

    TRUNCATE TABLE removes all rows from a table, but the table structure and its columns, constraints, indexes, and so on remain. To remove the table definition in addition to its data, use the DROP TABLE statement.

    SQL Truncate:

    The TRUNCATE TABLE command deletes the data inside a table, but not the table itself.

    Syntax:

    TRUNCATE TABLE table_name;

    SQL Drop:

    The DROP TABLE command deletes a table in the database.

    Syntax:

    DROP TABLE table_name;

    So truncating tables shall empty a table completely but drop table deletes a table in the database.

    Hence the correct answer is empty a table completely.

  • 5. Lock timeouts have which of the following advantages?
  • filter_dramaExplanation
    Answer is : D
    In lock timeout method, unnecessary rollbacks do not occur, transactions do not starve and it is also easy to implement and is hence widely used if transactions are short and long waits are likely to be due to deadlocks.

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