Some Useful DBMS Interview Questions Answers

What is an attribute?
ANSWER:
It is a particular property, which describes the entity.

What is a Relation Schema and a Relation?
ANSWER:
A relation Schema denoted by R(A1, A2, …, An) is made up of the relation name R and the list of attributes Ai that it contains. A relation is defined as a set of tuples. Let r be the relation which contains set tuples (t1, t2, t3, ..., tn). Each tuple is an ordered list of n-values t=(v1,v2, ..., vn).

What is degree of a Relation?
ANSWER:
It is the number of attribute of its relation schema.

What is Relationship?
ANSWER:
It is an association among two or more entities.

What is Relationship set?
ANSWER:
The collection (or set) of similar relationships.

What is Relationship type?
ANSWER:
Relationship type defines a set of associations or a relationship set among a given set of entity types.

What is degree of Relationship type?
ANSWER:
It is the number of entity type participating.

What is Data Storage - Definition Language?
ANSWER:
The storage structures and access methods used by database system are specified by a set of definition in a special type of DDL called data storage-definition language.

What is DML (Data Manipulation Language)?
ANSWER:
This language that enable user to access or manipulate data as organised by appropriate data model.
• Procedural DML or Low level: DML requires a user to specify what data are needed and how to get those data.
• Non-Procedural DML or High level: DML requires a user to specify what data are needed without specifying how to get those data.

What is DML Compiler?
ANSWER:
It translates DML statements in a query language into low-level instruction that the query evaluation engine can understand.

What is Query evaluation engine?
ANSWER:
It executes low-level instruction generated by compiler.

What is DDL Interpreter?
ANSWER:
It interprets DDL statements and record them in tables containing metadata.
.

What is Relational Algebra?
ANSWER:
It is procedural query language. It consists of a set of operations that take one or two relations as input and produce a new relation.


What is Relational Calculus?
ANSWER:
It is an applied predicate calculus specifically tailored for relational databases proposed by E.F. Codd. E.g. of languages based on it are DSL ALPHA, QUEL.