Question

$query=$this->db->query('SELECT g.gallery_id, g.gallery_title, (
                           SELECT i.gallery_image_path
                           FROM nepal_gallery_image AS i
                           WHERE i.gallery_id = g.gallery_id
                           AND i.gallery_image_status =  "Enabled"
                           LIMIT 0 , 1) AS gallery_image_path
                         FROM nepal_gallery AS g
                         WHERE g.gallery_status =  "Enabled"');

上述查询提供了正确的输出。

但是，当我使用CI子查询库时：

$this->load->library('Subquery');
$this->db->select('g.gallery_id,g.gallery_title');
$sub = $this->subquery->start_subquery('select');
$sub ->select('i.gallery_image_path')
     ->from('nepal_gallery_image AS i')                 
     ->where(array('i.gallery_image_status'=>"Enabled",  
                   'i.gallery_id'=>"g.gallery_id")) 
     ->limit(0,1);
$this->subquery->end_subquery('gallery_image_path'); 
$this->db->from('nepal_gallery AS g');
$this->db->where('g.gallery_stats',"Enabled");
$query=$this->db->get();

生成的查询是：

SELECT `g`.`gallery_id` , `g`.`gallery_title` , (
  SELECT `i`.`gallery_image_path`
  FROM (`nepal_gallery_image` AS i)
  WHERE `i`.`gallery_image_status` = 'Enabled'
  AND `i`.`gallery_id` = 'g.gallery_id'
  LIMIT 0 , 1 ) AS gallery_image_path
FROM (`nepal_gallery` AS g)
WHERE `g`.`gallery_status` = 'Enabled'

并且输出不符合预期。

第一个查询中的输出是

    <table>
     <tr>
         <th> gallery_id</th>
         <th> gallery_title</th>
         <th> gallery_image_path </th>
     </tr>
     <tr>
        <td>1</td>
        <td>Gallery 1</td>
        <td>images/image1.jpg</td>
     </tr>
     <tr>
        <td>2</td>
        <td>Gallery 2</td>
        <td>images/image2.jpg</td>
     </tr>
     </table>

但是，在以后的查询中，输出是

    <table>
     <tr>
         <th> gallery_id</th>
         <th> gallery_title</th>
         <th> gallery_image_path </th>
     </tr>
     <tr>
        <td>1</td>
        <td>Gallery 1</td>
        <td>NULL</td>
     </tr>
     <tr>
        <td>2</td>
        <td>Gallery 2</td>
        <td>NULL</td>
     </tr>
     </table>

似乎问题在于子查询。

有人可以帮我解决这个问题吗？

Answer 1

问题在于条件将表格别名g作为字符串'g.gallery_id'的子查询避免CI保护字段的一种方法是将第三个参数作为false传递给where条件，这样CI就不会尝试用反引号保护你的字段或表名。

试试这个

 $sub ->select('i.gallery_image_path')
 ->from('nepal_gallery_image AS i')                 
 ->where(array('i.gallery_image_status'=>"Enabled",  
               'i.gallery_id'=>"g.gallery_id"), NULL, FALSE);
                                           //--^^^^^^^^^^^^^^--here 
 ->limit(0,1);

或简单地写下你的条款manaully

  $where = "i.gallery_id = g.gallery_id AND i.gallery_image_status =  'Enabled'";
  $sub ->select('i.gallery_image_path')
 ->from('nepal_gallery_image AS i')                 
 ->where($where,NULL,FALSE); 
 ->limit(0,1);

Answer 2

 ->where(array('i.gallery_image_status'=>"Enabled",  
               'i.gallery_id'=>"g.gallery_id"))

问题在于'i.gallery_id'=＆gt;“g.gallery_id” - CI正在使用“g.gallery_id”构建查询，因为它是一个文字字符串...当它是一个表列引用时。如果您手动将“g.gallery_id”替换为“g”。“gallery_id”，则应将其作为演示。

如果您不知道如何解决这个问题，请发表评论。（这可能仅仅是使用单引号的问题。）

CodeIgniter子查询的问题

2 个答案: