mysql数据库连接怎么写

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

public class MySQLConnection {
    public static void main(String[] args) {
        // 数据库连接信息
        String url = "jdbc:mysql://localhost:3306/db_name";
        String username = "username";
        String password = "password";
        
        // 加载MySQL数据库驱动
        try {
            Class.forName("com.mysql.jdbc.Driver");
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        }
        
        // 建立数据库连接
        try {
            Connection connection = DriverManager.getConnection(url, username, password);
            // 进行数据库操作
            // ...
            
            // 关闭数据库连接
            connection.close();
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}

import mysql.connector

# 数据库连接信息
config = {
    'user': 'username',
    'password': 'password',
    'host': 'localhost',
    'database': 'db_name',
    'port': '3306'
}

# 建立数据库连接
try:
    connection = mysql.connector.connect(**config)
    cursor = connection.cursor()
    
    # 进行数据库操作
    # ...
    
    # 关闭数据库连接
    cursor.close()
    connection.close()
except mysql.connector.Error as error:
    print("Failed to connect to MySQL database: {}".format(error))

<?php
// 数据库连接信息
$servername = "localhost";
$username = "username";
$password = "password";
$dbname = "db_name";

// 建立数据库连接
try {
    $conn = new PDO("mysql:host=$servername;dbname=$dbname", $username, $password);
    $conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
    
    // 进行数据库操作
    // ...
    
    // 关闭数据库连接
    $conn = null;
} catch(PDOException $e) {
    echo "Failed to connect to MySQL database: " . $e->getMessage();
}
?>