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RDBMS Interview Questions - Part 1


What is database ?

A database is a logically coherent collection of data with some inherent meaning, representing some aspect of real world and which is designed, built and populated with data for a specific purpose.

What is DBMS ?

It is a collection of programs that enables user to create and maintain a database. In other words it is general-purpose software that provides the users with the processes of defining, constructing and manipulating the database for various applications.

What is a Database system ?

The database and DBMS software together is called as Database system.

Advantages of DBMS ?

  • Redundancy is controlled.
  • Unauthorised access is restricted.
  • Providing multiple user interfaces.
  • Enforcing integrity constraints.
  • Providing backup and recovery.

    Disadvantage in File Processing System ?

  • Data redundancy & inconsistency.
  • Difficult in accessing data.
  • Data isolation.
  • Data integrity.
  • Concurrent access is not possible.
  • Security Problems.

    Describe the three levels of data abstraction ?

    The are three levels of abstraction:
  • Physical level: The lowest level of abstraction describes how data are stored.
  • Logical level: The next higher level of abstraction, describes what data are stored in database and what relationship among those data.
  • View level: The highest level of abstraction describes only part of entire database.

    Define the "integrity rules"

    There are two Integrity rules.
  • Entity Integrity: States that "Primary key cannot have NULL value"
  • Referential Integrity: States that "Foreign Key can be either a NULL value or should be Primary Key value of other relation."

    What is extension and intension ?

  • Extension - It is the number of tuples present in a table at any instance. This is time dependent.
  • Intension - It is a constant value that gives the name, structure of table and the constraints laid on it.

    What is System R? What are its two major subsystems ?

    System R was designed and developed over a period of 1974-79 at IBM San Jose Research Center. It is a prototype and its purpose was to demonstrate that it is possible to build a Relational System that can be used in a real life environment to solve real life problems, with performance at least comparable to that of existing system. Its two subsystems are
  • Research Storage
  • System Relational Data System.

    How is the data structure of System R different from the relational structure ?

    Unlike Relational systems in System R
  • Domains are not supported
  • Enforcement of candidate key uniqueness is optional
  • Enforcement of entity integrity is optional
  • Referential integrity is not enforced

    RDBMS Interview Questions - Part 2 >>>




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