Php 如何连接MySQL表

我需要向查询中添加一个附加联接，但我不确定要在什么上联接它

SELECT DISTINCT * FROM {$this->prefix}category c 
   LEFT JOIN {$this->prefix}category_description cd 
      ON (c.category_id = cd.category_id) 
   LEFT JOIN {$this->prefix}category_to_store c2s 
      ON (c.category_id = c2s.category_id) 
WHERE c.category_id = '" . (int)$category_id . "' 
   AND cd.language_id = '" . (int)$this->config->get('config_language_id') . "' 
   AND c2s.store_id = '" . (int)$this->config->get('config_store_id') . "' 
   AND c.status = '1' 

我现在需要通过如下列值加入我的url\u别名表：

SELECT keyword FROM {$this->prefix}url_alias 
WHERE query = 'category_id=" . (int)$category_id . "'

--编辑以澄清--

这适用于OpenCart项目，该项目需要通过向现有类别/产品/制造商查询中添加关键字来简化url重写。

如何：

SELECT DISTINCT * FROM {$this->prefix}category c 
  LEFT JOIN {$this->prefix}category_description cd 
    ON (c.category_id = cd.category_id) 
  LEFT JOIN {$this->prefix}category_to_store c2s 
    ON (c.category_id = c2s.category_id) 

  LEFT JOIN {$this->prefix}url_alias u 
    ON u.query = CONCAT('category_id=', c.category_id)

WHERE c.category_id = '" . (int)$category_id . "' 
  AND cd.language_id = '" . (int)$this->config->get('config_language_id') . "' 
  AND c2s.store_id = '" . (int)$this->config->get('config_store_id') . "' 
  AND c.status = '1' 

这个怎么样：

SELECT DISTINCT * FROM {$this->prefix}category c 
  LEFT JOIN {$this->prefix}category_description cd 
    ON (c.category_id = cd.category_id) 
  LEFT JOIN {$this->prefix}category_to_store c2s 
    ON (c.category_id = c2s.category_id) 

  LEFT JOIN {$this->prefix}url_alias u 
    ON u.query = CONCAT('category_id=', c.category_id)

WHERE c.category_id = '" . (int)$category_id . "' 
  AND cd.language_id = '" . (int)$this->config->get('config_language_id') . "' 
  AND c2s.store_id = '" . (int)$this->config->get('config_store_id') . "' 
  AND c.status = '1' 

---

否表中没有类别_id的列。我应该说得更清楚些，我会修改这个问题。url_别名表中的列是

query

，该列中的行值是

category_id=12

，

product_id=345

等。好的，我编辑了答案，以便根据连接字符串进行连接测试。请注意，根据MySQL文档，很漂亮！康卡特我没想到，非常感谢彼得。非常好。不，表中没有类别id的列。我应该说得更清楚些，我会修改这个问题。url_别名表中的列是

query

，该列中的行值是

category_id=12

，

product_id=345

等。好的，我编辑了答案，以便根据连接字符串进行连接测试。请注意，根据MySQL文档，很漂亮！康卡特我没想到，非常感谢彼得。工作完美。