mySQL在codeigniter上的分层查询

Question

我试图从这个表中使用slu get获得结果的麻烦。

| id | parent | slug  | name  | 
----------------------------------------- 
| 1 | 0  | animations | animations | 
| 2 | 1  | flash  | flash  | 
| 3 | 2  | looped  | looped  | 
| 4 | 1  | gif  | gif images | 

例如，我需要获取父类为“动画”并且子类为“flash”的类别。

真正的问题是因为我需要使用category/$ parent_slug/$ child_slug来代替使用ID（category/$ id）来搜索结果|3|2|looped|looped|。

这是我到目前为止：

function get_category_childrens($category_parent=null){ 
    $this->db->select('*'); 
    if(!is_null($category_parent)){ 
     $this->db->where('categories.slug', $category_parent); 
     $this->db->join('categories as l1', 'l1.parent = categories.id', 'left'); 
    } 
    else{ 
     $this->db->where('categories.parent', '0'); 
    } 
    $query = $this->db->get('categories'); 
    return $query->result_array(); 
} 

生成的SQL：

SELECT * 
FROM (`categories`) 
LEFT JOIN `categories` as l1 ON `l1`.`parent` = `categories`.`id` 
WHERE `categories`.`slug` = 'animations' 

，如果你不知道CI，如果你的查询或它的一个想法，请没问题评论。

Answer 1

SELECT * 
FROM (`categories` as l1) 
LEFT JOIN `categories` as l2 ON `l2`.`parent` = `l1`.`id` 
LEFT JOIN `categories` as l3 ON `l3`.`parent` = `l2`.`id` 
WHERE `l1`.`slug` = 'animations' 
AND `l2`.`slug` = 'flash' 

Answer 2

SELECT categories.* 
FROM categories 
LEFT JOIN categories AS parent ON categories.parent = parent.id 
LEFT JOIN categories AS child ON categories.id = child.parent 
WHERE (parent.name='animations') and (child.name = 'flash') 

是我想你以后。