select
service.libelle||' '||to_char(date_envoi,'DD/MM/YYYY')  as envoi,
avis.libelle||' du '||to_char(date_retour,'DD/MM/YYYY')  as retour,
to_char(date_limite,'DD/MM/YYYY')  as limite
from consultation inner join service on service.service = consultation.service 
left join avis on avis.avis=consultation.avis
where consultation.dossier = '&idx'