Hey, Chad,
While it's true that ADO.NET doesn't offer full-blown SQL statements, there are filtering capabilities that *can* span multiple datatables, if a relation is set between the tables and the tables are part of the same dataset.
You may have to write a few lines of code to do so (or if it's too complex, you may have to do it in the back-end database.
If you're still interested in at least trying this out, can you provide some details on what you're trying to do?
Thanks,
Kevin