如何在php中按日期(日)对MySQL值进行分组？

<?php
$servername = "your_servername";
$username = "your_username";
$password = "your_password";
$dbname = "your_dbname";

// 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);
}

// 查询并按日期分组
$sql = "SELECT DATE(date) AS day, value FROM table_name GROUP BY day";
$result = $conn->query($sql);

if ($result->num_rows > 0) {
    // 输出数据
    while($row = $result->fetch_assoc()) {
        echo "日期: " . $row["day"]. " - 值: " . $row["value"]. "<br>";
    }
} else {
    echo "0 结果";
}

// 关闭连接
$conn->close();
?>