Question

我试图实施薪资系统并遇到一些问题。该程序需要能够从mysql db检索数据到jtextfield。

当我尝试搜索时，我得到并且错误地说＆＃34; com.mysql.jdbc.exception.jdbc4.MySQLSyntaxErrorException。您的SQL systax中有错误;查看与您的MySQL服务器版本对应的手册，以便在＃＆quot;＆＃39;附近使用正确的语法。在第1行＆＃34;

package AppPackage;

import java.sql.*;
import javax.swing.*;
import java.awt.event.*;
import java.util.logging.Level;
import java.util.logging.Logger;

public class AllowanceGUI extends javax.swing.JFrame {

Connection conn=null;
PreparedStatement pst=null;
ResultSet rs=null;

public AllowanceGUI() {
    initComponents();
}

private void formWindowOpened(java.awt.event.WindowEvent evt) {                                  
    conn=MySQLConnect.ConnectDb();
}                                 

private void SearchButtonActionPerformed(java.awt.event.ActionEvent evt) {                                             


    try {
        String sql = "SELECT EmployeeID,FirstName,LastName,Designation,BasicSalary FROM EmployeeInfo WHERE EmployeeID =?";
        pst=conn.prepareStatement(sql);
        pst.setString(1,EmployeeIDSearchField.getText());

        rs = pst.executeQuery(sql);
    while(rs.next()) { 
        EmployeeIDField.setText(rs.getString("EmployeeID"));
        FirstNameField.setText(rs.getString("FirstName"));
        LasNameField.setText(rs.getString("LastName"));
        DesignationField.setText(rs.getString("Designation"));
        BasicSalaryField.setText(rs.getString("BasicSalary"));



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

}}

我的数据库连接如下;

包AppPackage;

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

public class MySQLConnect {
Connection conn = null;
public static Connection ConnectDb(){

    try{
    Class.forName("com.mysql.jdbc.Driver");
    Connection conn = DriverManager.getConnection("jdbc:mysql://Localhost/easypay","root","");
    return conn;
    }catch(Exception e){
    JOptionPane.showMessageDialog(null, e);
    return null;

    }
}
}

任何人都可以帮我解释一下这段代码吗？

Answer 1

你正在做什么

   pst=conn.prepareStatement(sql);// Prepare this sql query for me
    pst.setString(1,EmployeeIDSearchField.getText());// Attach this value as first parameter
    rs = pst.executeQuery(sql);// IGNORE EVERYTHING, Execute this query

你应该在第三行做pst.executeQuery();。

修改

完全阅读了这是一个选择的事实。你应该在没有字符串查询的情况下执行executeQuery。附：为了更快的速度，使用列索引（整数）而不是rs.next（）循环中的列名。

Answer 2

终于找到了错误。

private void SearchButtonActionPerformed(java.awt.event.ActionEvent evt) {                                             


    try {
        String sql = "SELECT EmployeeID,FirstName,LastName,Designation,BasicSalary FROM EmployeeInfo WHERE EmployeeID =?";
        pst=conn.prepareStatement(sql);
        pst.setString(1,EmployeeIDSearchField.getText());

        rs = pst.executeQuery();
    if(rs.next()) { 
        String ID = rs.getString("EmployeeID");
        EmployeeIDField.setText(ID);
        String FN = rs.getString("FirstName");
        FirstNameField.setText(FN);
        String LN = rs.getString("LastName");
        LasNameField.setText(LN);
        String Des = rs.getString("Designation");
        DesignationField.setText(Des);
        String BS = rs.getString("BasicSalary");
        BasicSalaryField.setText(BS);

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

}

}

将数据从mysql db检索到textfield

2 个答案: