Hi Rao,

Database testing of a Web-based application would basically deal with Integrity checks as well updation checks of the Database.

Like gettoknow pointed out - for instance we have an web-application dealing with Order booking, we might have different functionalities associated with the same like -
1) Registered User ID
2) Number of Items Ordered
3) The pricing of each Item
4) Total calcualtion etc.

For each of these operations different tables in the DB would be getting updated. DB testing would basically involve -

1) Taking a snapshot of the Database tables in terms of number of records
present before carrying out the transaction
2) Taking a snapshot after functionality is carried out using the UI. The
number of records count should have gone up
3) checking if Relational dependency of tables is properly getting executed.
In sense when Orders table is updated, the inventorty table of the item
should reflect a decrease in that specified item
4) checking if intermediate updations occur in the DB prior to completion of
the specified functionality. This should not happen

These are the generic test scenarios. Other scenrios would be based more on test specification / functional specifications....

Cheers...