Explain ER Relationship model?
An entity-relationship model (ERM): An entity-relationship model (ERM) is an abstract theoretical illustration of structured data. Entity-relationship modelling is a relational schema database modelling techniques, used in software engineering to produce a kind of conceptual data model (or semantic data model) of a system, frequent a relational database, and its needs in a top-down fashion. Diagrams created using this procedure are known as entity-relationship diagrams, or ER diagrams or ERDs for short.