create function GetNumberOfRentalsCurrentlyAllowed(accountID int)
returns int

begin
    return (select accttype from Account_Types where accountID= accountID) - (select Row_NUMBER() Over (Partition By accountID Order By accountID, bookID
            from rentals
            where accountID = @accountID and checkedout=1 and checkedin=0), 0)
end

create VIEW RentalsRequested
as
select *, Row_NUMBER() Over (Partition By accountID Order By accountID, bookID) as numberOfRentalsRequested
from rentals
WHERE Rentals.checkedout = 0 AND Rentals.checkedin = 0