Question: What are the first names of all students who are taking classes from both the accounting department and the Computer Info. Systems department?
SQL: SELECT T1.stu_fname FROM student AS T1 JOIN enroll AS T2 ON T1.stu_num   =   T2.stu_num JOIN CLASS AS T3 ON T2.class_code   =   T3.class_code JOIN course AS T4 ON T3.crs_code   =   T4.crs_code JOIN department AS T5 ON T5.dept_code   =   T4.dept_code WHERE T5.dept_name   =   'Accounting' INTERSECT SELECT T1.stu_fname FROM student AS T1 JOIN enroll AS T2 ON T1.stu_num   =   T2.stu_num JOIN CLASS AS T3 ON T2.class_code   =   T3.class_code JOIN course AS T4 ON T3.crs_code   =   T4.crs_code JOIN department AS T5 ON T5.dept_code   =   T4.dept_code WHERE T5.dept_name   =   'Computer Info. Systems'