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.
Example of one-to-one relationship
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:
challenge see if you can find out one extra fact on this topic that we haven't already told you
Click on this link: One-to-one relationship