JDBC编程

之前不小心把所有代码都给删了，还清空了回收站，所以就写这个来保存代码了

• JDBC
• • 1.更新数据和查询
  • 2.PreparedStatement用法

代码如下（示例）：

import java.sql.*;

public class JDBC {
    public static final String URL = "jdbc:mysql://localhost:3306/mydatabase";
    public static final String userName = "root";
    public static final String password = "123456";
    public static void main(String[] args) throws ClassNotFoundException, SQLException {

        Class.forName("com.mysql.cj.jdbc.Driver");
        Connection con = DriverManager.getConnection(URL, userName, password);
        Statement stat = con.createStatement();
        String sql = "update mytable set userage = 100 where username = 'ncu'";
        PreparedStatement psmt = con.prepareStatement(sql);
        psmt.executeUpdate();//数据更新
        ResultSet rs = stat.executeQuery("select * from mytable");
        //要在数据更新后再查找，否则得到的不是更改后的数据
        while (rs.next()) {
            System.out.print("用户ID：t" + rs.getString("userID")+'t');
            System.out.print("用户名称:t " + rs.getString("username")+'t');
            System.out.println("用户年龄: t" + rs.getString("userage"));
        }
        con.close();
    }
}

代码如下（示例）：

import java.sql.*;

public class JDBCInsert {
    public static final String URL = "jdbc:mysql://localhost:3306/mydatabase";
    public static final String userName = "root";
    public static final String password = "123456";
    public static void main(String[] args) throws ClassNotFoundException, SQLException {

        Class.forName("com.mysql.cj.jdbc.Driver");
        Connection con = DriverManager.getConnection(URL, userName, password);
        Statement stat = con.createStatement();
        String sql = "insert into mytable (userid, username, userage) value (?, ?, ?)";
        String s1 = "005";
        String s2 = "lalala";
        String s3 = "90";
        PreparedStatement psmt = con.prepareStatement(sql);
        psmt.setString(1,s1);
        psmt.setString(2,s2);
        psmt.setString(3,s3);
        psmt.executeUpdate();//数据更新
        ResultSet rs = stat.executeQuery("select * from mytable");
        //要在数据更新后再查找，否则得到的不是更改后的数据
        while (rs.next()) {
            System.out.print("用户ID：t" + rs.getString("userID")+'t');
            System.out.print("用户名称:t " + rs.getString("username")+'t');
            System.out.println("用户年龄: t" + rs.getString("userage"));
        }
        con.close();
    }
}

上面的s1,s2,s3都可以自己输入