30 Basic Easy DBMS aptitude Questions 2007/08

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

Q What is a Relation Schema & a Relation?
A relation Schema denoted by R(A1, A2, …, An) is made up of the relation name
R & 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).
It is the number of attribute of its relation schema.



Q What is an Extension of entity type?
The collections of entities of a particular entity type are grouped together into an
entity set.

Q What is Weak Entity set?
An entity set may not have sufficient attributes to form a primary key, & its
primary key compromises of its partial key & primary key of its parent entity, then it is
said to be Weak Entityset


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

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

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


QWhat is an Entity?
It is a 'thing' in the real world with an independent existence.

Q What is an Entity type?
It is a collection (set) of entities that have same attributes.

Q What is an Entity set?
It is a collection of all entities of particular entity type in the database.

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