private void supprimer(Exercice exercice, String BASE) {
        if(!load()) return;
        try {
            String matieres = "";
            for(Matiere matiere:exercice.getMatieres())
                matieres += "','" + matiere.getNom();
            matieres = matieres.substring(3);
            int id = s.executeQuery(String.format(
                    "SELECT ID FROM %s WHERE NOM='%s' AND SUJET='%s' AND NIVEAU='%s' AND " +
                    "(SELECT MATIERE_ID FROM MAT_%s WHERE EXERCICE_ID = ID) = " +
                    "(SELECT         ID FROM MATIERES WHERE NOM IN (%s))",
                    BASE, exercice.getNom(), exercice.getSujet(), exercice.getNiveau().toString(),
                    BASE, matieres)).getInt("ID");
            s.executeUpdate(String.format("DELETE FROM %s WHERE ID=%d", BASE, id));
            s.executeUpdate(String.format("DELETE FROM MAT_%s WHERE EXERCICE_ID=%d", BASE, id));
        }
        catch(Exception e) {
            System.err.println(e.getClass().getName() + ": " + e.getMessage());
        }
    }