Database: college_1
Question: What is the last name of the student who got a grade A in the class with code 10018.
SQL: select t1.stu_lname from student as t1 join enroll as t2 on t1.stu_num  =  t2.stu_num where t2.enroll_grade  =  'a' and t2.class_code  =  10018