6. One-to-one relationships

For the purposes of ERD, we ignore history or what might happen in the future and we concentrate only with the now.

Think about a husband and wife.

A husband can only have one wife

A wife can only have one husband

this would be known as a 'one-to-one relationship'

This relationship can be portrayed diagramatically as:

one to one relationship

challenge see if you can find out one extra fact on this topic that we haven't already told you