Find the title of course whose prerequisite is course Differential Geometry.
create table prereq (course_id varchar, prereq_id varchar, PRIMARY KEY (course_id)); create table course (title varchar, course_id varchar, PRIMARY KEY (title)); create table course (course_id varchar, title varchar, PRIMARY KEY (course_id))
select title from course where course_id in (select t1.course_id from prereq as t1 join course as t2 on t1.prereq_id = t2.course_id where t2.title = 'differential geometry')