hi, i'm still in the process of studying decision stream. i already have a business problem to resolve though. we need to generate a report that retrieves data from an oracle database (snowflake schema). the report lists all countries grouped by region, and their GDP growth rate. to get this GDP growth rate, i need to have current year's GDP and the previous year's GDP of each country. how do i do derive the previous year's GDP? this may be simple to experts but for decision stream beginners like me, i'm at a loss. i would have easily done this through a SQL statement but how do i implement this in decision stream. pls help. thanks!