Mysql 是否完成SQL查询？新手

我已经有了这个代码，但是我想知道如何或者是否有可能扩展查询，这样我就可以总结每个用户的汽油使用量，这样我就可以看到谁消耗了最多的燃料，而不是现在，因为我得到了他们每次加油的总清单

<?php
include 'connection.php';
// Check if session is not registered, redirect back to main page. 
// Put this code in first line of web page. 
session_start();
if (!isset($_COOKIE["user"])) {
header("location:login.php");
}

include 'menu.php';
//start the blue background and the user bar on top of the page
echo "<div class=\"bluebox\">";
echo "<div class=\"datagrid\"><table width=\"100%\" cellspacing=\"0\" cellpadding=\"5\" border=\"0\">";
echo "<thead><tr><th>Brukernavn</th><th>Fullt navn</th><th>Sted</th><th>Liter</th><th>Dato</th></tr></thead><tbody>";

    $color1 = "#E1EEf4";
    $color2 = "#FFFFFF";
    $row_count = 0;

function getContent() {
    include 'connection.php';
        $query = "SELECT * FROM members JOIN diesel ON diesel.userid = members.id ORDER BY diesel.liter DESC";
        $sql=$oDB->prepare($query);
        $sql->execute();
        $row = $sql->fetchAll();
    return $row;
    //Row Colors setting

    }       
    error_reporting(E_ALL); ini_set('display_errors', 1);


$data = getContent();
foreach($data as $row) {
    $name = $row['username'];
    $fname = $row['name'];
    $sted = $row['sted'];
    $liter = $row['liter'];
    $dato = $row['dato'];

    $row_color = ($row_count % 2) ? $color1 : $color2;

     print "<tr bgcolor=\"$row_color\"><td>".$name."</td><td>".$fname."</td><td>".$sted."</td><td>".$liter."</td><td>".$dato."</td></tr>";
    $row_count++;
     }



echo "</tbody></table></div>";

?>

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感谢阅读：）复活节快乐

使用

SUM（）

和

groupby

很容易做到这一点

SELECT
  m.username,
  sum(d.liter) AS TOT_LITERS
FROM
  members m
    JOIN
  diesel d ON (d.userid = m.id)
GROUP BY m.username
ORDER BY 2 DESC;

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参考资料：

谢谢，我想我需要工会之类的东西。我想我需要更多的练习：）