使用数据库中的数据显示每日增长

Question

我有一个 table，我在其中存储我使用 PHP 从 API 获得的数据，table 看起来像这样：

ID	count	timestamp
6285	123	21.11 18:54
6284	122	21.11 18:53
6283	121	21.11 18:52
6282	120	21.11 18:51

我想要实现的是：在过去的 24 小时内，数字增加了 X

要从我使用的数据库中检索数据：

 while($row = mysqli_fetch_array($result))
{
// generating HTML table etc
// echo-ign data with $row['timestamp']
}

我的想法是在24小时内获得第一次写入和最后一次写入并获得差异，但我无法将这个想法转移到PHP

Answer 1

自 v.8.0 以来的现代 MySQL 版本提供了 window functions 这样的 'FIRST_VALUE':

SELECT DISTINCT
    DATE(`timestamp`) as day,
    FIRST_VALUE(`count`) OVER (PARTITION BY DATE(`timestamp`) ORDER BY `timestamp`) as start_day_count,
    FIRST_VALUE(`count`) OVER (PARTITION BY DATE(`timestamp`) ORDER BY `timestamp` DESC) as end_day_count
FROM t;

PHP 解决方案可以是下一个（使用PDO模块）：

<?php
$query = "
    SELECT DISTINCT
        FIRST_VALUE(`count`) OVER (PARTITION BY DATE(`timestamp`) ORDER BY `timestamp`) as start_day_count,
        FIRST_VALUE(`count`) OVER (PARTITION BY DATE(`timestamp`) ORDER BY `timestamp` DESC) as end_day_count
    FROM t WHERE DATE(`timestamp`) = '2021-11-21';";

$stmt = $pdo->prepare($query);
$stmt->execute();
$row = $stmt->fetch(PDO::FETCH_ASSOC);

print_r($row);

在这里你可以test PHP with MySQL window functions

或使用 mysqli:

<?php
$query = "
    SELECT DISTINCT
        FIRST_VALUE(`count`) OVER (PARTITION BY DATE(`timestamp`) ORDER BY `timestamp`) as start_day_count,
        FIRST_VALUE(`count`) OVER (PARTITION BY DATE(`timestamp`) ORDER BY `timestamp` DESC) as end_day_count
    FROM t WHERE DATE(`timestamp`) = '2021-11-21';";

$result = mysqli_query($mysqli, $query);

$row = mysqli_fetch_array($result);

print_r($row);

PHP mysqli demo

Answer 2

我们可以说“我想要过去 24 小时的最大计数和最小计数之间的差值”吗？计数总是在增加吗？

建议：

SELECT MAX(count) - MIN(count) AS up_24h
FROM your_table
WHERE timestamp >= NOW() - INTERVAL (24 * 60) MINUTE

使用数据库中的数据显示每日增长

Displaying the daily increase using data from the database

php

mysql

window-functions

mysql-8.0