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DATA RELATIONSHIPS

There are three types of data relationships that you should be aware of:

One-to-one (1:1) - A one-to-one relationship signifies that each instance of a given entity relates to exactly one instance of another entity. For example, each student would have exactly one grade record, and each grade record would be specific to one student.

One-to-many (1:M) - A one-to-many relationship signifies that each instance of a given entity relates to one or more instances of another entity. For example, one professor entity could be found teaching several classes, and each class could in turn be mapped to one professor.

Many-to-many (M:N) - A many-to-many relationship signifies that many instances of a given entity relate to many instances of another entity. To illustrate, a schedule could be comprised of many classes, and a class could be found within many schedules.