Which professors do have a Ph.D. degree?
select * from professor where prof_high_degree = 'Ph.d.'
How many of those professors are in each department?
select count(*), dept_code from professor where prof_high_degree = 'Ph.d.' group by dept_code
Find the code of the department that has the most of them.
select dept_code from professor where prof_high_degree = 'Ph.d.' group by dept_code order by count(*) desc limit 1
What is the name of that department?
select t2.dept_name from professor as t1 join department as t2 on t1.dept_code = t2.dept_code where t1.prof_high_degree = 'Ph.d.' group by t1.dept_code order by count(*) desc limit 1