Before we talk about the relational model in more detail, let us first define some very basic terms used in this model.
Tuple
Every row in a table shows a record and is called a tuple. A table containing 'n' attributes in a record is called n-tuple.
Attribute
The name of every column in a table is used to interpret its meaning and is known as an attribute. Every table is called a relation.
For instance, Figure shows a relation PERSON. The columns NAME, PERSON_ID, AGE and ADDRESS are the attributes of PERSON and every row in the table represents a separate tuple (record).
Relation Name: PERSON
|
PERSON_ID
|
NAME
|
AGE
|
ADDRESS
|
TELEPHONE
|
|
1
|
Sanjay Prasad
|
35
|
b-4,Modi Nagar
|
011-25347527
|
|
2
|
Sharad Gupta
|
30
|
Pocket 2, Mayur Vihar.
|
023-12245678
|
|
3
|
Vibhu Datt
|
36
|
c-2, New Delhi
|
033-1601138
|
Figure: An extended PERSON relation