ER Diagram Elements, Pros & Cons

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E lements and Pros Cons
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Introduction to ER Diagram
Elements to ER Diagram Pros Cons of ER Diagram
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ER diagram stands for Entity Relationship
diagram and is a graphical representation of
relations between the entities that are reserved
in database and supporting tables mapping.
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ENTITY
Strong Entity
Weak Entity key Attribute Simple Attribute
Composite Attribute Multivalued Attribute
Derived Attribute
ATTRIBUTES
RELATIONSHIP
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1.
An entity is anything that stores or contain
data. Entity is formed with attributes which are
present in that entity. Strong entity The entity
which have primary key and is presented by a
symbol of rectangle is strong entity. Weak
entity The ones which do not have enough
attributes to form a primary key. It is
presented by a symbol of double rectangle.
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The properties that describes the entity and its
type is attribute. It is represented by a symbol
of Eclipse.

• Key Attribute
• The attribute that exclusively recognizes each
  entity is called Key attribute.
• Simple Attribute
• The attribute that cannot be divided is called as
  simple attribute.

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Composite Attribute
Composite Attributes are the ones that can be
divided further. Multivalued Attribute The
attribute that contains more than one value is
multivalued attribute. Derived Attribute The
attribute whose value can only be derived from
other attribute is called as Derived attribute.
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Relationship describes or connection between the
entity sets and two entities.
Types of Relationships in ER-Diagram One-to-one
Relationship One-to-many Relationship Many to
one Relationship Many-to-Many Relationship
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Pros Simple
ER-Diagram is simple and easy to design. You just
need to collect data and put it on the right
place. Finest Visual Representation The data
represented in ER-Diagram is well structured and
has a finest visual representation that is easy
to understand. Effectual Communication ER-Diagram
enhances communication and is the effective tool
for developer with better understanding of
information.
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Cons
Finite Specification and Constraints The
constraints and the specifications in ER-Diagram
are limited as not every details are
entered. Mislaying of Information Some or many
information can be lost or are hidden in ER-
Diagrams. Lack of Data Manipulation
Representation Representation of Data
Manipulation is very hard in ER-Diagram also it
is used for high-level designing.
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