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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