ดร.เฟรดเดอริก คอนราดเคยสอนชั้นเรียนใดบ้าง ?ไม่จำเป็นต้องใช้ตารางทั้งหมด
Which classes has Dr. Frederick Conrad taught previously ?It is not neccessary to use all the tables.
 program_requirement:  program_id [ int]  category [ varchar]  min_credit [ int]  additional_req [ varchar] 
SELECT DISTINCT course.department, course.name, course.number FROM course, course_offering, instructor, offering_instructor WHERE course_offering.semester < (SELECT SEMESTERalias0.semester_id FROM semester AS SEMESTERalias0 WHERE SEMESTERalias0.semester = 'WN' AND SEMESTERalias0.year = 2016) AND course.course_id = course_offering.course_id AND instructor.name LIKE '%Frederick Conrad%' AND offering_instructor.instructor_id = instructor.instructor_id AND offering_instructor.offering_id = course_offering.offering_id