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Relations can be represented as
two-dimensional data tables with rows and columns
The rows of a relation are called
tuples.
The columns of a relation are
called attributes.
The attributes draw values from a
domain (a legal pool of values).
The number of tuples in a
relation is called its cardinality while the number of attributes in a relation
is called its degree
A relation also consists of a
schema and an instance
Schema defines the structure of a
relation which consists of a fixed set of attributedomain pairs.
An instance of a relation is a
time-varying set of tuples where each tuple consists of attribute-value pairs.
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