What are different ways to test databases?

Database testing should be kept simple. Database testing would include:

- Database Sandboxes
A sandbox is defined as a technical environment whose scope is well defined and respected. There are various types of sandboxes which can be used to work. In each sandbox, the database is copied. The new functionalities are implemented, existing functionality are refactored, validated in development sandbox and once you are satisfied with work, it gets shifted to project integration sandbox. In project integration sandbox, system is rebuild and tests are run to ensure nothing is wrong.
The advantage of sandboxes is that it helps to reduce the technical errors adversely affecting large number of people.

- Writing database tests
Writing database tests include setting up the test, running the tests using database regression testing tool and checking the results by comparing the current values against the results that you expected.

- Setting up strategies for database tests
To know the state of the database, put the database in known state before running the test suite. Common strategies for doing this is to start afresh and data reinitialization. Strategies for creating test data for writing database tests are having source test data, developing and maintaining test data creation scripts and self contained test cases.

- Database testing tools
There are two kind of database testing tools needed to test RDBMS: testing tools for interface tests and the other for internal database tests. Couple of things to remember here is that testing tools should support the language that you are developing in. Secondly, database should be put in a known state. Some database tetsing tools are:
Unit Testing Tools which enable you to regression test the database.
Load testing tools which simulate high usage loads on your database letting you know whether system's architecture can stand up to that level.
Test data generator are useful when large amounts of data is needed may be for stress and load testing.