Different types of attributes in dbms

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Each entity has a set of attributes associated with it. An attribute is a property or characteristics of an entity types that is of interest to the organization. The following are different types of entities



1. Single value attribute

Single value attribute means there is only one value associated with that attribute. The single value attribute is represented using ellipse symbol.

The examples of single value attributes are Adhara Number of a person, roll number of students, registration number of a car.

2. Multi value attribute

In case of multi value attribute more than one value will be associated with that attribute.

Consider an entity employee. An employee can have many skills; hence skills associated to an employee is multi valued attribute.

3. Derived attribute

A derived attribute is an attribute whose values can be calculated from the values of related attribute or entity. Derived attributed is represented using dotted ellipse.

Age of a person can be derived from the date of birth of the person. In this example "age" is the derived attribute and it is represented using dotted ellipse.

4. Null Attribute

In some cases, a particular entity may not have any applicable value for an attribute. For such situation, a special value called null value is created.

For example, in a table, there is one column called phone number. If a person do not have phone number then a null value is entered in that column.

6. Simple attributes

General attributes represents the characteristics of an entity.

7. Composite attribute 

Composite attribute is one which can be further subdivided into simple attributes or composite attribute is an attribute whose value is derived from its sub attributes.

The attribute address which can be further subdivided into street name, city, state and pin code.

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