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Introduction to
ER Model
ER model is represents real world
situations using concepts, which are commonly used by people. It allows
defining a representation of the real world at logical level.ER model has no
facilities to describe machine-related aspects.
In ER model the logical structure
of data is captured by indicating the grouping of data into entities. The ER
model also supports a top-down approach by which details can be given in
successive stages.
Entity: An entity is
something which is described in the database by storing its data, it may be a
concrete entity a conceptual entity.
Entity set: An entity set is
a collection of similar entities.
Attribute: An attribute
describes a property associated with entities. Attribute will have a name and a
value for each entity.
Domain: A
domain defines a set of permitted values for a attribute
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