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
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
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 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.
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
Databases related posts Visit HERE
Python-related posts Visit HERE
C++ related posts Visit HERE
Data Structures related posts visit HERE
Algorithms related posts visit HERE
Data Science related posts visit HERE