The primary key of a table may also be linked to a foreign key. This allows two tables to be linked. Special care must be taken while inserting data and removing data from the foreign key column.

For National 5 Computing Science, revise the use of primary and foreign keys and the difference between flat file and relational databases.

A foreign key is a relationship between two entities. Generally speaking, inter-entity relationships are one-to-many, e.g., an ORDER has many ORDER LINEs, and so forth. Even a case that may start out ...

The reference table may still exist, but instead of being used for all the FK references, a function or other processing could be defined that verifies a value’s existence. Retaining an infinitude of ...