--Find all Slytherin students with owls.
--select slast, sfirst from students where pet='Owl' and 
--house='Slytherin'

--Find all years where History of Magic was taught before noon.
--select * from courses where name='History of Magic' and
--starttime < 12

--Find all professors with a hyphen in their last name.
--select * from profs where plast like '%-%'

--Find all rooms with at least ten seats.
--select * from rooms where maxseats >= 10

--Find last names of all students who have ever failed a class.
--select distinct slast from grades where grade=0 order by slast desc



--Partner up all the Gryffindors and the Slytherins
--select s1.slast, s1.sfirst, s2.slast, s2.sfirst 
--from students s1, students s2
--where s1.house='Gryffindor' and s2.house='Slytherin'

--select students.slast, sfirst, crn, grade
--from grades join students on grades.slast=students.slast

--Write a query to retrieve a list of all courses with
--professor first & last names. (Table should have CRN, coursename,
--prof first name, prof last name)
--select crn, name, profs.plast, pfirst
--from courses join profs on courses.plast=profs.plast

--select students.sfirst, students.slast, grades.crn, 
--courses.name, grades.grade
--from grades join courses on grades.crn=courses.crn
--join students on students.slast=grades.slast

select sfirst, slast, crn, name, grade
from courses natural join grades natural join students