php 修复mysql数据表

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

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

// 检测连接
if ($conn->connect_error) {
    die("连接失败: " . $conn->connect_error);
}

// 添加一个新字段
$sql = "ALTER TABLE MyGuests ADD email VARCHAR(30)";
if ($conn->query($sql) === TRUE) {
    echo "新字段添加成功";
} else {
    echo "Error: " . $sql . "<br>" . $conn->error;
}

// 修改一个字段
$sql = "ALTER TABLE MyGuests MODIFY COLUMN lastname VARCHAR(50)";
if ($conn->query($sql) === TRUE) {
    echo "字段修改成功";
} else {
    echo "Error: " . $sql . "<br>" . $conn->error;
}

// 删除一个字段
$sql = "ALTER TABLE MyGuests DROP COLUMN address";
if ($conn->query($sql) === TRUE) {
    echo "字段删除成功";
} else {
    echo "Error: " . $sql . "<br>" . $conn->error;
}

// 优化表
$sql = "OPTIMIZE TABLE MyGuests";
if ($conn->query($sql) === TRUE) {
    echo "表优化成功";
} else {
    echo "Error: " . $sql . "<br>" . $conn->error;
}

$conn->close();
?>