Following is an ER diagram for a coffee shop. It illustrates the various internal and external entities involved in the system. The diagram also illustrates how these entities interact with one another and the relationship that exists between them. Here the entities are represented using square box shapes, the attributes using oval shapes, and the type of relationship using diamond-like shapes. Straight lines or links are used to connect different entities. The key attribute is represented using an underline. The cardinality among the various entities involved is also shown in this ER diagram.
