Can you Query DataTables?

Obviously you can fill a datatable from a query. Is it then possible to query that result set. I am tied into a really crappy old RDB database that only has access via ODBC. I'm working with maybe 5 or 6 tables. When I pull a whole table over, it takes maybe a minute for 150,000 records. Then however I have to use keys from that first table to query the other tables for data to build a complete dataset. To build a complete "record" for each of the 150,000 records in the first table, it takes over two hours. Can I just pull over all the records (so about 6 or 7 minutes), and run queries against them right in the Datatable, or do I have to dump them back to a SQL Server database or something?

Ok, nevermind, I see it.....:D

I'd see if there was a way to select fewer records in the first place.