Friday, 10 February 2012

Difference between data model and an entity relationship diagram?

  1. What is the difference between data model and an entity relationship diagram?
A data model is a model which shows how data is stored and used for e.g. a normal database It has 3 main parts1)Structural part:- how data is structured2)Integrity part:- Rules governing structure3)Manipulation part:- operators used to select,update,querry that data,eg select,update,delete commands in sqlTo furhter add Data Modelling is when we add this theory to Live instance.ENTERPRISE DATA MODEL(ENTERPRISE RELATIONSHIP MODELING) :- This can be called as an conceptual model or semantic model The sub parts of an ERM are1)Entity:- It is an object,eg employees,computer2) Relationship:- It captures how two or more entities are related to each other3)Attributes:- Every entity has its own sets of attributes (e.g. PAN no in India for each employee or SSN in US)To clarify the point look at eg A employee is an entity belonging to entity sets(All employees) which has a relationship with department, and attributes is emp code

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