java - 从数据库中检索总和

Question

       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);
        }

我无法从我的 PHANSONG 表中检索 soSV 的总和。它的结果是 0。当我尝试使用 String 而不是 int 时，它的结果是 null。有人能帮我吗？谢谢。

Image

Answer 1

我猜你需要在字符串文字之前添加 N 来处理 unicode 字符:

String sql = "SELECT SUM(soSV) AS sumSoSV FROM PHANCONG WHERE tenMH = N'Công nghệ phần mềm chuyên sâu'"