如何根据标准从RDD中的一系列记录中获取记录集？

I am new to Spark and I am struggling to resolve following problem with spark. I have a table which contains large number of records.Table contains student_id, course_id, risk_date, first_name, last_name. According to the business scenario there can be multiple risk_dates for one student_id and course_id. So I need to get the student_id, course_id, risk_date for for particular student_id and course_id with latest risk_date. I am new to Spark and I am struggling to resolv