DBMS Basics - Interview Questions and Answers

  1. What is Lossless join property?
    It guarantees that the spurious tuple generation does not occur with respect to relation schemas after decomposition.
  2. What is 1 NF (Normal Form)?
    The domain of attribute must include only atomic (simple, indivisible) values.
  3. What is Fully Functional dependency?
    It is based on 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.
  4. What is 2NF?
    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.
  5. What is 3NF?
    A relation schema R is in 3NF if it is in 2NF and for every FD X A either of the following is true
    1. X is a Super-key of R.
    2. A is a prime attribute of R.
    In other words, if every non prime attribute is non-transitively dependent on primary key.
  6. What is BCNF (Boyce-Codd Normal Form)?
    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.