功能SQL SUM查询

Question

我有数字的表是这样的：

______________________________________ 
| axle_id | train_id | axle | distance | 
|_________|__________|______|__________| 
| 1  |  1 | 1 | 20 | 
| 2  |  1 | 2 | 50 | 
| 3  |  1 | 3 | 200 | 
| 4  |  1 | 4 | 50 | 
| 5  |  1 | 5 | 200 | 
| 6  |  1 | 6 | 50 | 
| 7  |  1 | 7 | 200 | 
| 8  |  1 | 8 | 50 | 
|_________|__________|______|__________| 

现在我想指望他们，并与SUM计算。 的代码，我现在：

function count_axles($id) { 
     $sql = "SELECT sum(distance)/(25000)*(100) as totaldistance from axle WHERE train_id = :train_id"; 
     $sth = $this->pdo->prepare($sql); 
     $sth->bindParam(":train_id", $id, PDO::PARAM_STR); 
     $sth->execute(); 
     return $sth->fetchAll(); 
    } 

而且我通过调用这个函数：

<?php 
     $count_axle = $database->count_axles($_GET['train_id']); 
?> 
<?php  
    foreach($count_axle as $counting){ 
    } 

     echo $counting['totaldistance']; 
?> 

现在的输出是正确的。
（3.2800000000000002）这是25.000
的百分比，但我想补充5000，如：

$sql = "SELECT sum(distance)+(5000)/(25000)*(100) as totaldistance from axle WHERE train_id = :train_id"; 

但是，当我这样做，输出随机生成类似：

为什么要这样做，我该如何解决这个问题？

Answer 1

基本数学。你做

     5000 
    sum(distance) + -------------- 
        25000 * 100 

当你真的想

sum(distance) + 5000 
    ------------------------ 
     25000 * 100 

尝试

SELECT (sum(distance)+(5000))/(25000)*(100) 
     ^--------------------^ 

代替。请注意额外的括号。

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Answer 2

尝试用：

$sql = "SELECT (sum(distance)+(5000))/(25000)*(100) as totaldistance from axle WHERE train_id = :train_id"; 

司拥有和操作偏好。