Relational Model

January 22, 2016 Share Like Labels: bet

Hi Folks,

Continuing with DBMS, we'll take up relational model today. Previous article on ER model can be found here ER Model.

Any query- shoot it in comments section!

Some important points to note here about attributes in a relation are as follows:

1. Each attribute of a relation has a name.

2. The set of allowed values for each attribute is called the domain of the attribute

3. Attribute values are required to be atomic i.e indivisible.

4. Domain is said to be atomic if all its members are atomic.

5. The special value NULL is a member of every domain.

6. A relation is a set of n tuples (a1, a2, a3...) where each attribute belongs to corresponding domain.

Relational Algebra

The basic operators used in relational algebra are as follows:

1. SELECT

It is used to obtain a subset of the tuples of a relation that satisfy a select condition. The SELECT operator is denoted by symbol σ (sigma). The syntax for SELECT statement would be as follows:

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Relational Model - DBMS