I'm adding a table and subclass table to my DB. (Subclass table = table where the primary key joins to the primary key of another table, to give extra row information to some subset of the rows ...

Sometime primary keys are obvious, for example a car license plate could be used to uniquely identify cars. Often, primary keys are less obvious and it is necessary to create a unique value ...

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