CREATE TABLE professor (emp_num VARCHAR(255), dept_code VARCHAR(255)); CREATE TABLE department (dept_code VARCHAR(255), dept_name VARCHAR(255)); CREATE TABLE CLASS (prof_num VARCHAR(255)); CREATE TABLE employee (emp_fname VARCHAR(255), emp_num VARCHAR(255))
What is the first names of the professors from the history department who do not teach a class.
    
SQL: SELECT T1.emp_fname FROM employee AS T1 JOIN professor AS T2 ON T1.emp_num = T2.emp_num JOIN department AS T3 ON T2.dept_code = T3.dept_code WHERE T3.dept_name = 'History' EXCEPT SELECT T4.emp_fname FROM employee AS T4 JOIN CLASS AS T5 ON T4.emp_num = T5.prof_num