This is a very common issue that people run into as they begin to use complex dataset objects in their .NET development work. This applies to ASP.NET as well as Winforms development work... even WPF.
If you've ever put together a complex join query in one of your TableAdapter objects and then in your code attempted to apply it to a DataTable object, you may have seen this warning and had no idea what to do about it:
The solution is simple. Open your XSD in design view and select on the background area (do not select a query or a TableAdapter).
Then in the properties pallet you will see a property named "EnforceConstraints". Set this property to False.
This option gives you the ability to provide dataset level constraints which are usually not necessary if your database backend has its own constraints.