Conceptual Database using ER

Question 1

Entity

Answer 1

It is an object in the real world.
Noun is a basis.
Represented by a rectangle

Question 2

Entity Set

Answer 2

It is a collection of similar entities.
Represented by a rectangle

Question 3

Relation

Answer 3

It is an association among the entity sets.
Verb is a basis.
Represented using a diamond

Question 4

Relationship Set

Answer 4

Set of similar relations

Question 5

Attribute

Answer 5

Which describes an object.
Represented by an oval/ellipse.

Question 6

Types of Attributes

Answer 6

1. Simple attribute
2. Composite attribute
3. Single valued attribute
4. Multi valued attribute
5. Stored attribute
6. Derived attribute
7. Key attribute
8. Descriptive attribute

Question 7

Degree of relationship

Answer 7

Specifies the number of ENTITIES participating in the relationship

Question 8

Types of relationships

Answer 8

Unary
Binary
N-ary

Question 9

Participation constraints

Answer 9

1. Total Participation
2. Partial Participation

Question 10

Total Participation

Answer 10

Each entity in E must participate in relation R
Mandatory Participation
Double lines

Question 11

Partial Participation

Answer 11

Each entity in E may or may not participate in relation R
Optional Participation
Single line

Question 12

Key Constraints

Answer 12

Primary Key Constraints
Foreign Key Constraints
Unique Key Constraints

Question 13

Cardinality Ratio

Answer 13

One - to - One
One - to - Many
Many - to - One
Many - to - Many

Question 14

One - to - One

Answer 14

Each entity in A is associated with at most one entity in B and Each entity in B is associated with at most one entity in A

Question 15

One - to - Many

Answer 15

Each entity in A is associated with zero or many entities in B and Each entity in B is associated with at most one entity in A.

Question 16

Many - to - One

Answer 16

Each entity in A is associated with at most one entity in B and Each entity in B is associated with zero or many entities in A.

Question 17

Many - to - Many

Answer 17

Each entity in A is associated with zero or many entities in B and Each entity in B is associated with zero or many entities in A.

Question 18

Weak Entity Set

Answer 18

Has no key attributes of its own
Must always participate totally
Cardinality b/w owner and weak set is always one to many
Key of owner + partial key –> used to identify weak entities.

Question 19

Class Hierarchy

Answer 19

Shows relationship b/w generalized and specialized sets.

Question 20

Aggregation

Answer 20

Relationship participating in another relationship.