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Entity Relationship Model (ER model) in DBMS
Entity-Relationship model (ER model)
- An effective system where data is organized into discrete categories called entities(different database tables)
ERmodelis an illustration of various entities in business and the relationship between them
- It is built during the analysis phase of the system development life cycle
- The ER model separates the information required in the business i.e it establishes a clear distinction between data that is useful and not useful for business operations
Key components of the ER model
It is a set of related information i.e nothing but a database table.
- It defines what type of data an entity is storing i.e different columns in a table
- For example, a student entity consists of student name, ID, marks as attributes
- An entity may contain any numbers of attribute but it must contain at least one attribute .
- It is defined as an association between entities links between different database tables for data accessing
- Several relationships may exist between the same entity basically 4 relationships are identified
- One to one
- One to many
- Many to one
- Many to many
- These relationships are nothing but the links between in a table to another table or set of tables so that data can be transferred and used from more than one table .
ER model benefits
- Provide a clear picture of the scope of information requirement
- Provides an easily understandable pictorial map for database design
- It offers an effective Framework for integrating multiple applications.