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Which of the following statements is FALSE?

  • Q. Which of the following statements is FALSE?
  • filter_dramaExplanation
    Answer is : A

    Option 1) A database relation can have more than one primary key, is a false statement.

    Explanation:-

    Every relation has at least one candidate key, because at least the combination of all its attributes has the uniqueness property. In the case of base relations (relations of a base table), one candidate key is designated as the primary key and the remaining candidate keys are called alternate keys.

    Key Points

    •  A database relation can have both primary key and secondary key.
    • A foreign key is an attribute or attribute combination of one relation(table) whose values are required to match those of the primary key of some other relation(table).
    • Also, the foreign key and the primary key should be defined on the same underlying domain.
    • A database relation can have more than one foreign key.
    • A candidate key is an attribute that can uniquely identify a row in a table.

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Similar Questions

  • 1. Which of the following is a collection of point to point links that form a round?
  • filter_dramaExplanation
    Answer is : C

    The correct option is (3)

    Concept:-

    Ring topology:- A ring network is a network topology in which each node connects to exactly two other nodes, forming a single continuous pathway for signals through each node. This type of topology is highly efficient and handles heavier loads better than bus topology.

    Key Points

    • A ring is a collection of point-to-point links that may form a circle.
    • Point-to-point topology is any network that connects two hosts in a dedicated fashion.
    •  In a point-to-point link, both the transmit and receive operation can occur over separate wires.
    • The most prominent example of point-to-point communication is a simple telephone call, where one phone is connected with another, and both nodes can send and receive audio.
    • Point-to-point internet connection is a wireless method of connecting to the internet over large areas without the need for extensive cabling.

    Additional InformationWAN topology:- A wide area network topology describes the layout of network components and connections on a given WAN. WAN topology using the star network configuration requires a central hub.

    MAN configuration:- A Metropolitan Area Network (MAN) is a network that connects two or more computers, communicating devices or networks in a single network that has a geographic area larger than that covered by even a large 'LAN' but smaller than the region covered by a 'WAN'.

    LAN configuration:- A local area network is a series of devices that are linked together in one physical location, like a house, office, or school. Home WiFi networks and small business networks are common examples of LANs.

     

  • 2. If a transaction has obtained a __________ lock, it can read but cannot write on the item
  • filter_dramaExplanation
    Answer is : A
    If a transaction Ti has obtained a shared-mode lock (denoted by S) on item Q, then Ti can read, but cannot write, Q.
  • 3.

    The subdivision of data link layer into two sub-layers: logical link control (LLC) and media access control (MAC) has been done by which of the following standard?

  • filter_dramaExplanation
    Answer is : C

    The correct answer is IEEE.

    Explanation:-

    IEEE: The world's largest technical organization. IEEE stands for Institute of Electrical and Electronics Engineers.

    Logical link layer(LLC) - This sub-layer describes under IEEE 802.2 standard, and its function is to identify network layer protocol.

    Media access control(MAC) - This sub-layer describes under IEEE 802.3 standard, this sub-layer tells us how the devices acquire the channel and transmit the data.

    ANSI: Stands for American national standards institute.

    ITU:  Stands for the International telecommunication union which manages things related to information and communication technology.

    PARC: Palo Alto Research Center is a research and development company.

  • 4. A transaction is made to wait until all ________ locks held on the item are released
  • filter_dramaExplanation
    Answer is : A
    A transaction is made to wait until all compatible locks held on the item are released. This ensures that no other transaction is concurrently accessing the same item.
  • 5. ______ clause allows sorting of query results by one or more columns.
  • filter_dramaExplanation
    Answer is : D
    DISTINCT

    DISTINCT statement is used to return only distinct (different) values.For Ex:

    SELECT DISTINCT column1, column2, ...
    FROM table_name;

    ALL

    ALL operator returns true if all of the subquery values meet the condition. For Ex:

    SELECT column_name(s)
    FROM table_name
    WHERE column_name operator ALL
    (SELECT column_name FROM table_name WHERE condition);

    WHERE

    The WHERE clause is used to extract only those records that fulfill a specified condition.

    For ex: SELECT column_name FROM table_name WHERE condition

    ORDER BY

    he ORDER BY keyword is used to sort the result-set in ascending or descending order.For Ex:

    SELECT column1, column2, ...
    FROM table_name
    ORDER BY column1, column2, ... ASC|DESC;
     

     

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