在codeigniter中转换复杂的JOIN查询

Question

我正在将我现有的网站转换为CI,并且我已经尝试了几天将此查询转换为CI友好代码:

$result = mysql_query("
    SELECT t1.mnumber, t1.mcontent, t1.mcontact
    FROM sms t1
    JOIN (
        SELECT mContent,mcontact, mnumber, MAX(mID) mID
        FROM sms
        GROUP BY mContact
    ) t2 ON t1.mcontact = t2.mcontact AND t1.mid = t2.mid
    GROUP BY t1.mContact
    ORDER BY t1.mid DESC
"); 

但无论我尝试什么,我都无法在CI上得到正确的结果.

我希望你们能在这里帮助我!

---

最接近我得到的结果,是当我使用子查询黑客时.然而,出于沮丧,我删除了代码块并继续尝试.

我决定使用平面查询,就像上面发布的那样.这几乎给了我结果.

$query = $this->db->query("SELECT t1.mnumber, t1.mcontent, t1.mcontact FROM sms t1
JOIN (SELECT mContent,mcontact, mnumber, MAX(mID) mID FROM sms GROUP BY mContact) t2
ON t1.mcontact = t2.mcontact AND t1.mid = t2.mid GROUP BY t1.mContact ORDER BY t1.mid DESC"); 


$contacts = array();

//Add data to our array
foreach($query->result() as $row){
     echo $row->mNumber;
}

return $contacts;

但是,在我看来,我收到通知"消息:未定义的属性:stdClass :: $ mNumber"

所以仍然没有结果,加上我更喜欢CI查询方法.

Answer 1

您可以像这样在codeigniter中使用它

$query = "  SELECT t1.mnumber, t1.mcontent, t1.mcontact
            FROM sms t1
            JOIN (
                SELECT mContent,mcontact, mnumber, MAX(mID) mID
                FROM sms
                GROUP BY mContact
            ) t2 ON t1.mcontact = t2.mcontact AND t1.mid = t2.mid
            GROUP BY t1.mContact
            ORDER BY t1.mid DESC"; 
$result =   $this->db->query($query);           
return $result->result();

第二种方法

您可以使用codeigniter的子查询方式为此目的执行此操作,您将不得不破解codeigniter.像这样.转到system/database/DB_active_rec.php从这些函数中删除public或protected关键字

public function _compile_select($select_override = FALSE)
public function _reset_select()

现在子查询写入可用现在这里是您的查询与活动记录

$select =   array(
                'mContent',
                'mcontact',
                'mnumber',
                'MAX(mID) mID'
            );
$this->db->select($select);
$this->db->from('sms');
$this->db->group_by('mContact');
$subquery = $this->db->_compile_select(); // get the query string

$this->db->_reset_select(); // reset so it can newly form the query

unset($select);
$select =   array(
                't1.mnumber',
                't1.mcontent',
                't1.mcontact'
            );
$this->db->select($select);
$this->db->join('',"($subquery)");
$this->db->from('sms t1');
$this->db->group_by('t1.mContact');
$this->db->order_by('t1.mid','DESC');
$result =   $this->db->get();
return $result->result();

事情已经完成了.干杯!!!注意:使用子查询时必须使用

$this->db->from('myTable')

代替

$this->db->get('myTable')

它运行查询.