[arvit]

Relational DBs work for processing of business transactions -- when you need to get the amount of money and all the other details exactly right, when you need to retrieve the right record according to a variety of criteria which may come from other types of data, and when you need to be sure the info is inserted in exactly the right format.

For this, there are DB transactions, SQL SELECT with joins, and schemas.

Much of this is possible in other technologies, but RDB does it well.