Logical Database using ER

Question 1

Relation Model ?

Answer 1

Collections of relations (Tables)

Question 2

Each Relations consists of what ?

Answer 2

Set of tuples (records/rows) &
Set of attributes (columns)

Question 3

Each Relation is described using ?

Answer 3

Schema &
Instance

Question 4

Describe Relation Schema

Answer 4

Specifies structure of the relation -

Name
Attribute
Type(Domain)
Constraints

Question 5

Describe Relation Instance

Answer 5

It is a TUPLE, basically a ROW form the entire relation/table.

Question 6

Degree (arity) of a Relation

Answer 6

Total number of ATTRIBUTES/COLUMNS

Question 7

Cardinality of a Relation

Answer 7

Total number of TUPLES/ROW

Question 8

Integrity Constraints

Answer 8

Condition specified on database schema.
Restriction on a tuple

Question 9

Types of Integrity Constraints

Answer 9

5 types -
1. Primary key
2. Unique
3. Not Null
4. Foreign Key
5. Check

Question 10

Super Key

Answer 10

Set of those keys that identify a row or a tuple uniquely
Super set of candidate key
Usually two tuples

Question 11

Candidate Key

Answer 11

Attribute or set of attribute
Identify each record uniquely
{ID} and {Name, DOB}.

Question 12

Primary Key

Answer 12

Identify each record uniquely
Can be only one attribute
Can be one per relation

Question 13

Foreign Key

Question 14

What does foreign key links

Answer 14

two tables/relations

Question 15

Table with foreign key

Answer 15

Referencing Table
Child Table

Question 16

Table using the foreign key as primary key

Answer 16

Referenced Table
Parent Table