Entity Relationship Model


Attribute is an Element of an Entity. Entity can design with one or more related Data Attributes. Attribute can categories into two types that Identifier and Descriptor. Identifier Attribute is called Key Attribute that specifies a unique value in the Entity to identify an instance of the transaction(s). Descriptor Attribute is called Non-Key Attribute that specifies a non-unique value in the Entity that describes more information about an instance of the transaction(s).

For example, Employee entity is defined with Emp_Code and Emp_Name attributes. Emp_Code is an Identifier attribute and Emp_Name is a Descriptor attribute of Employee Entity.

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