I've been using cyrstal reports in my projects. What has worked best for me is to bind the reports to DataSets and not the SQL Server database. I usualy start by creating a new dataset then adding the fields manual to it or draging them from the tables.
I shape the ds to fit my needs then when Im actualy using the reports i have a great deal of flexability in collecting the data. It also means that my reports are lossly coupled to the DB.