Find out the average salary of professors?
select avg ( salary ) from instructor
Find the average salary of the professors of each department?
select avg ( salary ), dept_name from instructor group by dept_name
Which department has the highest average salary of professors?
select dept_name from instructor group by dept_name order by avg ( salary ) desc limit 1
Which department has the lowest average salary of professors?
select dept_name from instructor group by dept_name order by avg ( salary ) limit 1
In which department Mr. Mird work for?
select dept_name from instructor where name = 'Mird'
How much is the salary Mr. Mird earns currently?
select salary from instructor where name = 'Mird'