how many departments are there?
select count(*) from department
show all their info.
select * from department
where are they each located?
select dlocation from department as t1 join dept_locations as t2 on t1.dnumber = t2.dnumber
what are the names of departments that are located in Houston?
select t1.dname from department as t1 join dept_locations as t2 on t1.dnumber = t2.dnumber where t2.dlocation = 'Houston'