# DBMS Basics Interview Questions and Answers For Freshers and Experience Part-5

**41. What is normalization?**

It is a process of analysing the given relation schemas based on their Functional Dependencies (FDs) and primary key to achieve the properties

(1).Minimizing redundancy, (2). Minimizing insertion, deletion and update anomalies.

**42. What is Functional Dependency?**

A Functional dependency is denoted by X Y between two sets of attributes X and Y that are subsets of R specifies a constraint on the possible tuple that can form a relation state r of R. The constraint is for any two tuples t1 and t2 in r if t1[X] = t2[X] then they have t1[Y] = t2[Y]. This means the value of X component of a tuple uniquely determines the value of component Y.

**43. What is Lossless join property?**

It guarantees that the spurious tuple generation does not occur with respect to relation schemas after decomposition.

**44. What is 1 NF (Normal Form)?**

The domain of attribute must include only atomic (simple, indivisible) values.

**45. 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.

**46. 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.

**47. 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

X is a Super-key of R.

A is a prime attribute of R.

In other words, if every non prime attribute is non-transitively dependent on primary key.

**48. 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.

**49. What is 4NF?**

A relation schema R is said to be in 4NF if for every Multivalued dependency X Y that holds over R, one of following is true.

1.) X is subset or equal to (or) XY = R.

2.) X is a super key.

**50. What is 5NF?**

A Relation schema R is said to be 5NF if for every join dependency {R1, R2, …, Rn} that holds R, one the following is true 1.) Ri = R for some i.

2.) The join dependency is implied by the set of FD, over R in which the left side is key of R.

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