Question: How many courses do the student whose id is 171 attend?
Schema: create table courses (course_id varchar, PRIMARY KEY (course_id)); create table student_course_attendance (course_id varchar, student_id varchar, PRIMARY KEY (course_id))
SQL: select count(*) from courses as t1 join student_course_attendance as t2 on t1.course_id = t2.course_id where t2.student_id = 171