Relationships for Dummies

[Pat Hartman]

Optional is just a word to describe a relationship that is not required. It doesn't mean that you can put invalid data in the field. Doing that would violate RI. All it means is that the field may or may not contain a FK, therefore, when you create a query with a join on that FK, the join MUST be a Left join unless you really only want to return records where the FK has a non-null value.