php - 获取多行并存储到变量。 MySQL 和 PHP

Question

我正在为我的系统创建一个平均公里运行计算器。所以我试图获取最后两个日期和最后两个在我的数据库上运行的日期。

这是我当前的代码:

<?php

$conn = mysqli_connect('localhost','root','','mypms');

 $sqldates = "SELECT dateinput FROM sched ORDER BY dateinput DESC LIMIT 2";
 $sqlrun = "SELECT reading FROM sched ORDER BY reading DESC LIMIT 2"; 

 $resultdate = mysql_query($conn,$sqldates);
 $resultrun = mysql_query($conn,$sqlrun);


 while($rowdate = mysql_fetch_assoc($resultdate))
 {
     this ->
 }

 $date_difference = $date2 - $date1;

 while($rowrun = mysql_fetch_assoc($resultrun))
 {
     this ->
 }

 $run_difference = $run2 - $run1;
 $averagerun = $run_difference/$date_difference

 echo $averagerun;
?>

我应该在 this 上写什么，以便我可以将 $resultrun 和 $resultdate 存储到 $date1、$date2 和 $run1、$run2。

注意:日期输入的日期类型是我的mysql数据库上的日期。

Answer 1

尝试此查询 - 它将返回您的结果

SELECT 
run_difference/date_difference AS averagerun
FROM
    (
        SELECT
        DATEDIFF(date2,date1) AS date_difference,
        reading2 - reading1 AS run_difference
        FROM
        (
            SELECT 
            (SELECT dateinput FROM sched ORDER BY dateinput LIMIT 0, 1) AS date1, 
            (SELECT dateinput FROM sched ORDER BY dateinput LIMIT 1, 1) AS date2,
            (SELECT reading FROM sched ORDER BY reading DESC LIMIT 0, 1) AS reading1,
            (SELECT reading FROM sched ORDER BY reading DESC LIMIT 1, 1) AS reading2 
            FROM DUAL
        ) t1
    )t2

或“单行”:

SELECT 
    (SELECT reading FROM sched ORDER BY reading DESC LIMIT 1, 1)-(SELECT reading FROM sched ORDER BY reading DESC LIMIT 0, 1)   /   DATEDIFF((SELECT dateinput FROM sched ORDER BY dateinput LIMIT 1, 1), (SELECT dateinput FROM sched ORDER BY dateinput LIMIT 0, 1))  AS averagerun
FROM DUAL