What is the course title of the prerequisite of course Mobile Computing?
create table course (title varchar, course_id varchar, PRIMARY KEY (title)); create table prereq (prereq_id varchar, course_id varchar, PRIMARY KEY (prereq_id)); create table course (course_id varchar, title varchar, PRIMARY KEY (course_id))
select title from course where course_id in (select t1.prereq_id from prereq as t1 join course as t2 on t1.course_id = t2.course_id where t2.title = 'mobile computing')