Table schema:
CREATE TABLE student (stu_num VARCHAR, stu_lname VARCHAR); CREATE TABLE enroll (class_code VARCHAR, stu_num VARCHAR); CREATE TABLE CLASS (crs_code VARCHAR, class_code VARCHAR)

Question: What is the code of the course which the student whose last name is Smithson took?
SQL: SELECT T1.crs_code FROM CLASS AS T1 JOIN enroll AS T2 ON T1.class_code = T2.class_code JOIN student AS T3 ON T3.stu_num = T2.stu_num WHERE T3.stu_lname = 'Smithson'