Referential Integrity

When two tables are linked with primary/foreign keys, it is important to maintain referential integrity.

In the movies example, every Movie record has a DirectorID that tells us which director directed the movie.

If we delete one of the directors, while one of the movies is supposedly directed by that person, the movie will point to a director who doesn’t exist. That would break referential integrity.

Referential integrity is the extent to which the data in both tables ‘matches’.

You will not be asked for a definition!

You could be asked what would happen if data in one table is removed or changed, or what kind of error could occur if data is removed or changed.