The Data Filter widget has a Query property that can be used as an input to query the resulting InfoTable from the
Servicequerying the database. You'll want to take a look at the InfoTableFunctions' Query()
Service(available from the +Snippets +tab) which takes an InfoTable and query object as inputs. Ideally, you'll implement it in such a way that you're querying the database once to retrieve the entire data set and further querying will be done on the resulting InfoTable.
What's your reasoning for wanting to populate a DataTable with data from a database? Why not use your existing database?