Introduction to ER Models

Two people stand at a whiteboard. One runs the college office and knows nothing about databases. The other has to build the system.

They cannot talk in SQL, and they cannot talk in vague English either. They need one drawing that both of them can point at and argue with.

That drawing is an entity relationship diagram.

The entity relationship model, usually shortened to ER model, is a way to draw data as boxes and lines before any table exists. Peter Chen proposed it in 1976, and it is still the notation most database courses and most design tools use.