public static boolean checkFeedback(String s_id, String i_id, int o_id) {
        try {
            
            Connection conn = global.getConnection();
            
            PreparedStatement pStmt = conn.prepareStatement("select student_id from takes where offering_id = ? and student_id = ?");
            pStmt.setInt(1, o_id);
            pStmt.setString(2, s_id);
            
            ResultSet rs = pStmt.executeQuery();
            if (!rs.next()) {
                pStmt.close();
                return true;
            }
            pStmt.close();
            
            pStmt = conn.prepareStatement("select instructor_id from teaches where offering_id = ? and instructor_id = ?");
            pStmt.setInt(1, o_id);
            pStmt.setString(2, i_id);
            rs = pStmt.executeQuery();
            
            if (!rs.next()) {
                pStmt.close();
                return true;
            }
            pStmt.close();
            
            pStmt = conn.prepareStatement("select count(*) from feedback where student_id = ? and instructor_id = ? and offering_id = ?");
            pStmt.setString(1, s_id);
            pStmt.setString(2, i_id);
            pStmt.setInt(3, o_id);
            
            rs = pStmt.executeQuery();
            
            if(rs.next()) {
                int count = rs.getInt(1);
                if (count == 0) {
                    pStmt.close();
                    return false;
                }
                pStmt.close();
                return true;
            }
            else {
                pStmt.close();
                return false;
            }
        }
        catch (ClassNotFoundException cnfe) {
            System.err.println("CNFE: " + cnfe.toString());
            return true;
        }
        catch (SQLException sqle) {
            System.err.println("SQLE: " + sqle.toString());
            return true;
        }
    }