Introduction to the Relational Model

Your ER diagram is finished. It has boxes, diamonds and ellipses on it.

None of those shapes is something a database can store.

What the database holds is tables. This chapter says exactly what a table is, which rules it must obey, and how your drawing becomes tables you can create.

Where the model came from

Before the relational model, a program reached a record by walking a path. The employee record sat at a known place on disk. The department record was reached through a pointer stored beside it.

That worked until something moved