Referencial integrity ensures that a reference which is non-null always refers to a valid record. The other record is however allowed to have any values for its attributes, including null values.
Referencial integrity ensures that a reference which is non-null always refers to a valid record. The other record is however allowed to have any values for its attributes, including null values.
Referencial integrity ensures that a reference which is non-null always refers to a valid record. Some records can, if you wish, not be referred to from another record. What is important is that all foreign keys are either null or refer to a valid record.
Referencial integrity ensures that a reference which is non-null always refers to a valid record. References (or foreign keys) can however be null.
Referencial integrity ensures that a reference which is non-null always refers to a valid record.
- a foreign key in a record always refers to another record which contains nulls
- a foreign key in a record always refers to another record which does not contain nulls
- a record is always referred to from another record
- a record can never contain a null value for a foreign key.
- a non-null foreign key attribute always refers to another record
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