create trigger chk_team 
on teams
for insert, update as
declare @chkCountry as char(2)
select @chkCountry = (select country from INSERTED)
-- if @@ROWCOUNT =0 RETURN
If @chkCountry NOT IN
	(select distinct country from teams)
BEGIN
	raiserror('Impossible country entered', 16, 1)
	ROLLBACK TRANSACTION
END