3. Benefits of relational databases

The main benefit of a relational database is that data doesn't have to be duplicated.

When a customer books an appointment for their pet, a new record is created on the 'appointment's table' and the relevant Customer and Pet IDs are chosen.

Reducing data duplication reduces the amount of data which needs to be stored, thus making the database smaller. It also reduces the risk of mistakes, because every time you have to type the same data in, there is a risk you could mis-spell it.