What is the first name of students who got grade C in any class?
create table student (stu_num varchar, PRIMARY KEY (stu_num)); create table enroll (stu_num varchar, PRIMARY KEY (stu_num))
select distinct stu_fname from student as t1 join enroll as t2 on t1.stu_num = t2.stu_num where enroll_grade = 'c'