这是获取和计算SQL数据的正确方法吗?

我是php和sql的新手。今天，我给自己的任务是从sql数据库中获取整数值，然后做一些基本的计算。是否有其他地方可以减少代码，同时仍然完成任务，或者我已经下降到最基本的水平?在这个过程中，我是否执行过度了?

我的目标是;

1. 从列中获取db值
2. 从本列中获取平均值
3. 然后计算排除最高值和最低值的新平均值。

下面是我最好的尝试;

$con = new MySQLi('localhost', 'user', 'pass', 'db_test') ;
    $count = $con->query('SELECT COUNT(SP$) FROM `math`');
    $grp = $con->query('SELECT GROUP_CONCAT(SP$) FROM `math`');
    $min = $con->query('SELECT MIN(SP$) FROM `math`');
    $max = $con->query('SELECT MAX(SP$) FROM `math`');
    $sum = $con->query('SELECT SUM(SP$) FROM `math`');
    $avg = $con->query('SELECT AVG(SP$) FROM `math`');
    $count = $count->fetch_assoc();
    $grp = $grp->fetch_assoc();
    $min = $min->fetch_assoc();
    $max = $max->fetch_assoc();
    $sum = $sum->fetch_assoc();
    $avg = $avg->fetch_assoc();
    $count = $count['COUNT(SP$)'];
    $grp = $grp['GROUP_CONCAT(SP$)']; 
    $min = $min['MIN(SP$)'];
    $max = $max['MAX(SP$)'];
    $sum = $sum['SUM(SP$)'];
    $avg = $avg['AVG(SP$)'];

显示和计算如下;

    echo "Sample Size: " . $count ."</br />";
    echo "Display Values:" . $grp ."</br />";
    echo "Sum of Values: " . $sum ."</br />";
    echo "Average: " . $avg ."</br /></br />";
    echo "Now find the new average, by excluding the highest and lowest value:";
    echo "Lowest Value: " . $min ."</br />";
    echo "Highest Value: " . $max ."</br />";
    echo "New Sum: " . ($sum - $max - $min) . "</br />";
    echo "New Average : " . (($sum - $max - $min) / ($count-2));