如何根据groupby Mysql Php进行数据抓取和合并

<?php
// 连接数据库
$servername = "localhost";
$username = "username";
$password = "password";
$dbname = "database";

$conn = new mysqli($servername, $username, $password, $dbname);
if ($conn->connect_error) {
    die("连接失败: " . $conn->connect_error);
}

// 编写SQL查询语句
$sql = "SELECT category, SUM(quantity) as total_quantity FROM products GROUP BY category";

// 执行SQL查询
$result = $conn->query($sql);

// 提取和合并数据
$data = array();
if ($result->num_rows > 0) {
    while ($row = $result->fetch_assoc()) {
        $category = $row["category"];
        $totalQuantity = $row["total_quantity"];

        // 数据处理和合并
        if (isset($data[$category])) {
            $data[$category] += $totalQuantity;
        } else {
            $data[$category] = $totalQuantity;
        }
    }
}

// 输出结果
foreach ($data as $category => $totalQuantity) {
    echo "分类: " . $category . "<br>";
    echo "总数量: " . $totalQuantity . "<br>";
    echo "<br>";
}

// 关闭数据库连接
$conn->close();
?>