数据库怎么连mysql

import mysql.connector

# 创建连接
conn = mysql.connector.connect(
  host="localhost",
  user="username",
  password="password",
  database="databasename"
)

# 创建游标
cursor = conn.cursor()

# 执行查询
cursor.execute("SELECT * FROM table")

# 获取结果
result = cursor.fetchall()

# 关闭连接
cursor.close()
conn.close()

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

public class Main {
    public static void main(String[] args) {
        Connection conn = null;
        Statement stmt = null;
        ResultSet rs = null;
        try {
            // 创建连接
            conn = DriverManager.getConnection(
                    "jdbc:mysql://localhost:3306/databasename?user=username&password=password");

            // 创建语句
            stmt = conn.createStatement();

            // 执行查询
            rs = stmt.executeQuery("SELECT * FROM table");

            // 处理结果
            while (rs.next()) {
                // 处理每一行数据
            }
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            // 关闭资源
            try {
                if (rs != null) {
                    rs.close();
                }
                if (stmt != null) {
                    stmt.close();
                }
                if (conn != null) {
                    conn.close();
                }
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }
}

<?php
$servername = "localhost";
$username = "username";
$password = "password";
$dbname = "databasename";

// 创建连接
$conn = new mysqli($servername, $username, $password, $dbname);

// 检查连接是否成功
if ($conn->connect_error) {
    die("连接失败: " . $conn->connect_error);
}

// 执行查询
$sql = "SELECT * FROM table";
$result = $conn->query($sql);

// 处理结果
if ($result->num_rows > 0) {
    while($row = $result->fetch_assoc()) {
        // 处理每一行数据
    }
}

// 关闭连接
$conn->close();
?>