Pour executer ce fichier : 
sql>@drop.txt


drop table visa;
drop table pays;
drop table personne;

drop type visa_type;
drop type personne_type;
drop type enfant_nt_type;
drop type enfant_elt_nt_type;
drop type pays_type;
drop type telephone_vry_type;
drop type telephone_elt_vry_type;
drop type adresse_type;