What is the prerequisite for Mobile computing?
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' )
What is the department name for these courses?
select dept_name 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' )
How many courses are there in the History Department?
select count ( * ) from course where dept_name = "History"