SELECT c.Nom,COUNT(v.Identifiant)
    FROM VIDEOS v
    LEFT JOIN EMISSION e ON e.Nom=v.E_Nom
    LEFT JOIN CATEGORIE c ON c.Nom=e.Categorie
    LEFT JOIN HISTORIQUE h ON h.V_Id=v.Identifiant
    WHERE sysdate-h.Date_Visionnage <= 14
    GROUP BY c.Nom;