Conceptual Database Design with ER Model

Conceptual Database Design with ER Model is one of the most important topic in Databases. Whenever a programmer wants to develop a database the ER Model is the basic thing he starts with.

ER Model Def. ER Model shows relations between the objects/entities in a database. Wikipedia definition of ER Model HERE. There are three basic things in an ER model

  • Entity
  • Attributes
  • Relationships

Why to Use ER Model?

  • Helps in defining terms related to entity relationship modeling.
  • build logical tables
  • ER Model Helps in making relational tables and they further help to make a whole database.
  • Works as a blueprint for a database.

Symbols in ER Model

conceptual database design with er model

Entity

In Conceptual database design with ER model entity is a real world physically recognizable thing. For example we are creating a database of a bank management. In a bank management database system an employee is an entity, customer is entity and manager/admin is also an entity.

Attribute

Attribute is basically a characteristic of an entity. For example if there is a customer’s account in a bank, so customer being an entity he has has attributes like bank account number, name, age, etc. There are 4 types of attributes

  • Simple attribute: Can’t be broken down further. For example ATM card code.
  • Composite attribute : Can be broken down further. Name of person can be broken down into first, middle and last name.
  • Derived attribute: an attribute derived from other attributes. For example age of the person can be derived from his date of birth.
  • Multivalued attribute: If a person has two phone numbers then for the same attribute he he has two values.

Relationship

In a database there is a connection between two entities which is known as relationship. For example in bank database management system Between Bank and Customer there is Relationship of account. A person x has an account in bank y is a relationship

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