Weak Entity Types

A college runs a course called Math 101. That course has several sections: Section 1, Section 2, Section 3.

Try to identify one of them by its own attributes. "Section 1" is not enough, because Physics 202 has a Section 1 as well.

Only the pair works: Math 101, Section 1. The section cannot be identified without naming the course it belongs to.

An entity that cannot be identified by its own attributes alone is a weak entity. It depends on another entity, called its owner or strong entity, for identification.

The four properties

**It has no key of its own