Stephen Ramsey points out that Relational Databases are very helpful and very efficient to access and search data. All Rational Databases use a comprehensive language goes by SQL that enable users and applications to search data very faster and more accuracy comparing to digital archives.
The relation between tables in Relational Databases it very similar to real-world relationships. You don't have to try learn them. Because we are born with relations and everything around us has kind of a relation with the other objects. These relations name as "one-to-one", "one-to-many", "many-to-one" and "many-to-many". Because, Relational Databases designed based on idea of Unified Model Language (UML) that those above relations are fundamental of UML concepts. All the designed tables can be related together logically and very easy and you can modify these relations whatever you want. However, it's not easy to define these kinds of relations in Digital Archives or modify them easily.
Design and Access
Rational Databases force designers to specify data types and then design the correspondence tables. There are exist all kinds of data type like numeric, string, big string, stream/byte.... So, it's very easy to search data in specific tables (query) very efficient comparing with Digital Archives. To have a basic or an advanced search, Rational Databases do not involve all the tables always. So, you don't have to look up entire all tables. However, Digital Archive need to be explored most of the time entire the archives. Rational Databases, enable users to access the tables multiple levels (Admin, Users...). As a Database designer you can define the permission levels for everybody. So, all users do not have same access to all Database. It goes by access queries and searches. However, it's very hard to manage and define all these permissions in Digital Archives. It's very easy to modify and design tables in Rational Databases. Also, you can add, delete and update data (considering your permission) there. Also, some Rational Databases like Oracle has some mechanisms that you can access to your previous data even it has been deleted or modified. However, it's not very easy to update data in Digital Archives like Rational Databases.