Hi Spd,

Database Testing is basically done to validate the data that are created by the Application.

For example if you are creating data in the front end of the application either by entering manually or running an electronic file inorder to fetch the data then all these data will be recorded and saved in the database. You can also generate Reports and flat files based on different criterieas. Database testing in this case will be
1. validating the reports generated and the flat files against the Database.
2. To check the data created are saved in the database.
3. Reports and flat files are validated based on different business rules and conditions.

For database validation most of the times we will be using the DML. i.e., we will be retrieving the records using different conditional operators and Joins.
Some of the times you will also be inserting or updating the database, but in general the testers will not be having the access to the database for writing.