From the course: Relational Databases Essential Training

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Relationship optionality and cardinality

Relationship optionality and cardinality

From the course: Relational Databases Essential Training

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Relationship optionality and cardinality

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- [Instructor] Once two tables are related together, you can start to think about the minimum number of records that can be related and the maximum number. In relational database terminology, these are called optionality and cardinality. Optionality is a measure of the minimum number of records that can be associated between two ends of a relationship. This number is usually either zero or one, and it can be thought of as the difference between must and might. For example, if a customer must have at least one order, then the optionality is one. That indicates a situation where your business rules dictate a requirement that every customer has at least one order before their record can be created. The minimum number allowed is one, so the optionality is one. On the other hand, if a customer might have an order, the optionality is zero. This indicates a situation where a customer's record can be created before…

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