Write SQL for top student per department

You are given two tables, Departments and Students. Each row of Departments describes one department through its dept_id and dept_name. Each row of Students describes one student through student_id, student_name, an optional dept_id that points at a department, an optional gpa, and an enrolled_at date. Write one SQL statement that returns, for every department — including departments that have no students at all, and departments whose students all have a NULL gpa — the…