从数据库中检索总和

try{
            Class.forName("com.microsoft.sqlserver.jdbc.SQLServerDriver");        
            String url = "jdbc:sqlserver://localhost;databaseName=QLLTCK;integratedSecurity=true;";
            Connection connection = DriverManager.getConnection(url);
            String sql = "SELECT SUM(soSV) AS sumSoSV FROM PHANCONG WHERE tenMH = 'Công nghệ phần mềm chuyên sâu'";
            PreparedStatement pst = connection.prepareStatement(sql); 
            ResultSet rs = pst.executeQuery();
            if(rs.next()){
                int SumSoSV = rs.getInt("sumSoSV");
                JOptionPane.showMessageDialog(null,"Số sinh viên dự thi: " + SumSoSV);
            }
        }
       catch(Exception sqlex){
            JOptionPane.showMessageDialog(null, sqlex);
        }

我无法从PHANCONG表中检索soSV的总和。其结果为0。当我尝试使用String而不是int时，其结果为null。有人能帮我吗？谢谢。