CREATE TABLE STUDENT (Fname VARCHAR, StuID VARCHAR)
CREATE TABLE ENROLLED_IN (Fname VARCHAR, StuID VARCHAR)

Find the first name of students not enrolled in any course.
SELECT Fname FROM STUDENT WHERE NOT StuID IN (SELECT StuID FROM ENROLLED_IN)
SELECT "Fname" FROM "STUDENT" WHERE NOT "StuID" IN (SELECT "StuID" FROM "ENROLLED_IN")