I understand the need for database testing for systems integration testing to validate the dataflows.
What is the purpose of Db testing for UAT, Is it just to validate the data and the integrity of the data?
Data validation is a possible reason for including the database in UAT. However, it's most likely that the users will do their validation via the UI, not directly on the database. They're certainly not going to be looking at individual stored procedures or functions within the database except at the presentation layer.
The exception to that might be a reporting group, which utilizes extracts or similar techniques to gather data.
Generally speaking, however, users don't have direct access to the database.