CodeIgniter自加入不匹配SQL

Question

好的，必须在这里丢失一些东西。

我的SQL工作正常：

SELECT t1.id, t1.material, t2.id, t2.material, t3.id, t3.material, t4.id, t4.material 
FROM ml_levels t1 

LEFT JOIN ml_levels t2 
ON t1.parentID = t2.id 

LEFT JOIN ml_levels t3 
ON t2.parentID = t3.id 

LEFT JOIN ml_levels t4 
ON t3.parentID = t4.id 

WHERE t1.id = 286 

这将返回

id | material | id | material   | id | material   | id | material 
------------------------------------------------------------------------------------------- 
286 | 4Layer | 209 | Protective Film | 60 | Specialty Products | 1 | Protect 

然而，我的ActiveRecord只返回t4.id和t4.material：

$this->db->select('t1.id, t1.material, t2.id, t2.material, t3.id, t3.material, t4.id, t4.material'); 
    $this->db->from('ml_levels AS t1')->where('t1.id',286); 
    $this->db->join('ml_levels AS t2','t1.parentID = t2.id','left'); 
    $this->db->join('ml_levels AS t3','t2.parentID = t3.id','left'); 
    $this->db->join('ml_levels AS t4','t3.parentID = t4.id','left'); 

    return $this->db->get()->row(); 

这将返回：

id | material | 
------------------- 
1 | Protect | 

$这个 - > DB-> last_query（）返回：

SELECT `t1`.`id`, `t1`.`material`, `t2`.`id`, `t2`.`material`, `t3`.`id`, `t3`.`material`, `t4`.`id`, `t4`.`material` 
FROM (`ml_levels` AS t1) 
LEFT JOIN `ml_levels` AS t2 ON `t1`.`parentID` = `t2`.`id` 
LEFT JOIN `ml_levels` AS t3 ON `t2`.`parentID` = `t3`.`id` 
LEFT JOIN `ml_levels` AS t4 ON `t3`.`parentID` = `t4`.`id` 
WHERE `t1`.`id` = 286 

如果我在数据库上运行此SQL，它正好返回原来的查询返回了什么。

Answer 1

Codeigniter仅返回没有表格标签的字段名称，因此您只能找到两个字段，因为只有id和material。更改行：

$this->db->select('t1.id, t1.material, t2.id, t2.material, t3.id, t3.material, t4.id, t4.material'); 

有：

$this->db->select('t1.id AS t1id, t1.material AS t1material, t2.id AS t2id, t2.material AS t2material, t3.id AS t3id, t3.material AS t3material, t4.id AS t4id, t4.material AS t4material');