CodeIgniter子查詢的問題

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"'); 

上面的查詢給出了正確的輸出。

然而，當我使用CI子查詢庫：

$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(); 

結果查詢是：

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' 

，並沒有如預期的輸出。

在第一個查詢輸出

<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> 

然而，在後來的查詢，輸出是

<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> 

看來問題是子查詢。

任何人都可以幫助我嗎？

Answer 1

問題是子查詢的條件是把你的表別名g作爲字符串'g.gallery_id'避免CI保護字段的一種方法是通過在條件中傳遞第三個參數爲false，因此CI不會嘗試保護你的字段或錶帶反引號的名字。

試試這個

$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); 

或簡單的寫你的條款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")) 

問題是與「i.gallery_id」 =>「g.gallery_id」 - CI正在建設的查詢與「g.gallery_id」作爲一個字符串...當它奧特是一個表列參考。如果您手動將「g.gallery_id」替換爲「g」。「gallery_id」，它應該用作演示。

如果你不知道如何補救，請留下評論。 （這可能只是使用單引號的問題）。