Attributes in ER Diagram-

 

Before you go through this article, make sure that you have gone through the previous article on Introduction to ER Diagrams.

 

• Attributes are the descriptive properties which are owned by each entity of an Entity Set.
• There exist a specific domain or set of values for each attribute from where the attribute can take its values.

 

Types of Attributes-

 

In ER diagram, attributes associated with an entity set may be of the following types-

 

 

1. Simple attributes
2. Composite attributes
3. Single valued attributes
4. Multi valued attributes
5. Derived attributes
6. Key attributes

 

1. Simple Attributes-

 

Simple attributes are those attributes which can not be divided further.

 

Example-

 

 

Here, all the attributes are simple attributes as they can not be divided further.

 

2. Composite Attributes-

 

Composite attributes are those attributes which are composed of many other simple attributes.

 

Example-

 

 

Here, the attributes “Name” and “Address” are composite attributes as they are composed of many other simple attributes.

 

3. Single Valued Attributes-

 

Single valued attributes are those attributes which can take only one value for a given entity from an entity set.

 

Example-

 

 

Here, all the attributes are single valued attributes as they can take only one specific value for each entity.

 

4. Multi Valued Attributes-

 

Multi valued attributes are those attributes which can take more than one value for a given entity from an entity set.

 

Example-

 

 

Here, the attributes “Mob_no” and “Email_id” are multi valued attributes as they can take more than one values for a given entity.

 

5. Derived Attributes-

 

Derived attributes are those attributes which can be derived from other attribute(s).

 

Example-

 

 

Here, the attribute “Age” is a derived attribute as it can be derived from the attribute “DOB”.

 

6. Key Attributes-

 

Key attributes are those attributes which can identify an entity uniquely in an entity set.

 

Example-

 

 

Here, the attribute “Roll_no” is a key attribute as it can identify any student uniquely.

 

Next Article- Converting ER Diagrams to Tables

 

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