MYSQL语法错误 - Codeigniter函数计算成本 [英] MYSQL Syntax error - Codeigniter function to calculate cost

问题描述

function stationcost($station1,$station2)
{

    $data = array();


    $this->db->select('Zone')->from('station_zone')->where('Station', $station1);
    $Q = $this->db->get();

    $this->db->select('cost')->from('zone_cost')->where('zone', $Q);
    $query = $this->db->get();

    if ($query->num_rows() > 0)
    {
    foreach ($query->result() as $row)
    {
    $data = $row->Cost;
    return $data;
    }
} 
}

一个整数，该函数正确工作。

If i change $Q to an integer, the function works correctly. I'm yet to add another station to minus the difference to calculate the zone difference

将名称转换为区域
$ station2 - $ station1 ='computedfigure'

Convert names to zones $station2 - $station1 = 'calculatedfigure'

然后从zone_cost中选择成本，其中zone ='计算图';

Then select cost from zone_cost where zone = 'calculcated figure';

我的错误消息：

A Database Error Occurred

Error Number: 1064

You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '' at line 3

SELECT `cost` FROM (`zone_cost`) WHERE `zone` =

Filename: models/station_model.php

Line Number: 59

我试过了这个

$this->db->select('Zone')->from('station_zone')->where('Station', $station2);
    $S2 = $this->db->get();

     $this->db->select('Zone')->from('station_zone')->where('Station', $station1);
    $S1 = $this->db->get();

    $Q = $S2 - $S1;

推荐答案

问题是变量 $ Q 不包含有效值，可能是因为在 $ station1 中传递的值在数据库中不存在。

The problem is that the variable $Q does not contain a valid value, presumably because the value passed in $station1 does not exist in the database. I would have thought that CI would counter this by at least using an empty quoted string, but apparently not.

你需要验证 $ Q 在传递给 where（）之前具有合理的值。例如，另一个 num_rows（）检查将告诉您第一个查询是否找到任何东西。

You need to validate that $Q holds a sensible value before you pass it to where(). For example, another num_rows() check will tell you whether the first query found anything.

从 $ Q 传递字段数据，而不仅仅是对象。因此，在您的情况下， $ Q-> row（） - > Zone 。

Also, you need to pass the field data from $Q, not just the object. So in your case, $Q->row()->Zone.

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