What do you mean by Data Modelling?
Data modelling is an exercise to put the layout of the structured
data in a meaningful way so that respective business support systems can read
or write back their data. It gives birds eye view of how the business
application stores the data and explains about how the data flows behind the
scene.
What is entity, what is relationship and what is attribute?
Any place, class, object or person can be classified as entity. An
entity can end up being multiple physical tables in the database. For example,
Address can be an entity in conceptual data model and it can end up as Country
table, State table and City table in the physical model.
What are different types
of Data Modelling? What are the steps to build the data model?
There
are 3 main types of data model, 1. Conceptual 2. Logical 3. Physical.
Conceptual model talks about overall data and its relation in the system. It
also give us the information on how each entity is related to other entity and
what is its relation with other entity.
Where is Data Modelling used?
Wherever
the data is involved, there has to be data modelling. Sometimes if the
application is small then modeler directly prepares the physical data model. If
the system is large than it is advisable to have all the 3 (Conceptual, Logical
and Physical) data models. If the system is transactional (for example,
Ecommerce website) then Relational data modelling techniques are used. If the
system is Data Warehouse, then the dimensional data modelling techniques are
used.
