java查询mysql数据库ql语句

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;

public class DatabaseConnection {
    public static void main(String[] args) {
        // 数据库连接信息
        String url = "jdbc:mysql://localhost:3306/mydatabase";
        String username = "root";
        String password = "password";

        // 建立数据库连接
        try {
            Connection connection = DriverManager.getConnection(url, username, password);
            // 连接成功后可以进行数据库查询操作
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

public class DatabaseQuery {
    public static void main(String[] args) {
        // 数据库连接信息
        String url = "jdbc:mysql://localhost:3306/mydatabase";
        String username = "root";
        String password = "password";

        // 建立数据库连接
        try {
            Connection connection = DriverManager.getConnection(url, username, password);
            // 创建Statement对象
            Statement statement = connection.createStatement();
            // 执行查询语句
            String query = "SELECT * FROM mytable";
            ResultSet resultSet = statement.executeQuery(query);
            
            // 处理查询结果
            while (resultSet.next()) {
                // 从ResultSet中提取数据
                int id = resultSet.getInt("id");
                String name = resultSet.getString("name");
                // ... 其他列
                
                // 打印或处理提取的数据
                System.out.println("id: " + id + ", name: " + name);
            }
            
            // 关闭结果集和Statement
            resultSet.close();
            statement.close();
            
            // 关闭数据库连接
            connection.close();
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}