数据库错误。sql。SQLEception:参数索引超出范围（1>参数数，为0）

Question

我是编程新手，不知道如何修复这个错误：java。sql。SQLEception:参数索引超出范围（1>；参数数，即0）。第一个JFrame运行时，我收到一条消息，它已连接到数据库，但随后弹出错误，没有任何内容保存到我的数据库中。 这是我的密码：

import java.sql.*;
import javax.swing.*;

public class SaveData extends javax.swing.JFrame {
Connection conn=null;
PreparedStatement pst=null;
ResultSet rs=null;

public SaveData() {
    initComponents();
}                 

private void btnSaveActionPerformed(java.awt.event.ActionEvent evt) {                                        
   conn=MySQLConnect.ConnectDB();
   String Sql="Select * from TripData";
   try{
       pst=conn.prepareStatement(Sql);
       pst.setString(1, txtTripDate.getText());
       pst.setString(2, txtStartDest.getText());
       pst.setString(3, txtEndDest.getText());
       pst.setString(4, txtMileage.getText());
       pst.setString(5, txtCost.getText());
       if(rs.next()){
           JOptionPane.showMessageDialog(null, "Trip Saved");
           InfoSaved s=new InfoSaved();
           s.setVisible(true);
       }
       else{
           JOptionPane.showMessageDialog(null, "Invalid Information", 
"Please enter again", JOptionPane.ERROR_MESSAGE);

       }
   }catch(Exception e){
       JOptionPane.showMessageDialog(null, e);       }
}                                       

Answer 1

SQL字符串必须包含-要设置的每个参数的占位符

Answer 2

我认为你想做这样的事情[如果pst是一种声明，那么它是有效的]：

    private void btnSaveActionPerformed(java.awt.event.ActionEvent evt) {                                        
        conn=MySQLConnect.ConnectDB();
        String Sql="Select * from TripData";
        try{
            pst = conn.createStatement(ResultSet.TYPE_SCROLL_SENSITIVE, ResultSet.CONCUR_UPDATABLE);
            rs = pst.executeQuery(Sql); // Gets all the TripData rows
            rs.moveToInsertRow();       // Moves to "insert" row
            // Updates "insert" row columns
            rs.updateString("colum_name", txtTripDate.getText()); 
            rs.updateString("colum_name", txtStartDest.getText());
            rs.updateString("colum_name", txtEndDest.getText());
            rs.updateString("colum_name", txtMileage.getText());
            rs.updateString("colum_name", txtCost.getText());
            rs.insertRow(); // Inserts the "insert" row to your database
            if(rs.rowInserted()){
                JOptionPane.showMessageDialog(null, "Trip Saved");
                InfoSaved s=new InfoSaved();
                s.setVisible(true);
            }
            else{
                JOptionPane.showMessageDialog(null, "Invalid Information", "Please enter again", JOptionPane.ERROR_MESSAGE);
        }
        }catch(Exception e){
            JOptionPane.showMessageDialog(null, e);       
        }
    }

编辑： [pst代码作为准备的报表]
您必须更改查询，不能通过SELECT order插入（如果您希望这样做）

private void btnSaveActionPerformed(java.awt.event.ActionEvent evt) {                                        
    conn=MySQLConnect.ConnectDB();
    String Sql="INSERT INTO TripData(COLUMN_NAME, COLUMN_NAME, COLUMN_NAME, COLUMN_NAME, COLUMN_NAME) VALUES(?, ?, ?, ?, ?)";
    try{
        pst = conn.prepareStatement(Sql);
        pst.setString(1, txtTripDate.getText()); 
        pst.setString(2, txtStartDest.getText());
        pst.setString(3, txtEndDest.getText());
        pst.setString(4, txtMileage.getText());
        pst.setString(5, txtCost.getText());
        int affectedRows = pst.executeUpdate();
        if(affectedRows != 0){
            JOptionPane.showMessageDialog(null, "Trip Saved");
            InfoSaved s=new InfoSaved();
            s.setVisible(true);
        }
        else{
            JOptionPane.showMessageDialog(null, "Invalid Information", "Please enter again", JOptionPane.ERROR_MESSAGE);
    }
    }catch(Exception e){
        JOptionPane.showMessageDialog(null, e);       
    }
}

对不起，我弄错了