to write algebra expression, you need to use rename, assignment and cartesian product. In addition, you need to use extended relational algebra operators, groupby and aggregate.

Part 2. Translation between sql statement, relation algebra and expression: We use the following database schema: Sailors (sid, sname, rating, age) Reserves (sid, bid, date) Boats (bid, bname, color) 3. Write the sql statement and relation algebra for: Find the name of sailer who has made the second most number of the reservation on the red boats