Almost every application you interact with over the Internet is backed by a database of some sort. Databases house the data needed by the application. Such data is then retrieved and converted to a form required by the graphical user interface (GUI) by a middleware to display to the end user. Depending on the application needs and business logic, some data may be created, updated, and deleted from the database.

Sometimes, it is necessary to directly test databases outside the application(s) that use it. This may help identify database bottlenecks such as expensive table joins, missing table indexes, slow running queries, and so on.