Prasanna,

I am also new to Reporting Services, but have had a similar issue in populating a chart and table - which only allow a single dataset to be tied to it.  If you cannot build a query using joins to return a single resultset containing all the fields needed for your chart/table, then, you may have to write a stored procedure which returns the data you need from a temp table.  The stored procedure can contain your various queries which populate a temp table - and then have the stored proc return or select those fields needed by your Reporting Services object.