Question

如何转换左连接包括select to codeigniter sql方法？谢谢。我只是想知道。

SELECT c1.c1_id, c1.c1_name, c2.c2_id, c2.c2_name, c2.c2_type, c2.c2_status, f.f_id, f.f_name, f2.f2_id, f2.f2_name FROM category2 c2 
LEFT JOIN category1 c1 ON c1.c1_id = c2.c1_id 
LEFT JOIN (
    SELECT DISTINCT c2_id, f_id, f_name FROM file ORDER BY f_id DESC
) f ON f.c2_id = c2.c2_id
LEFT JOIN (
    SELECT DISTINCT c2_id, f2_id, f2_name FROM file2 ORDER BY f2_id DESC
) f2 ON f2.c2_id = c2.c2_id
WHERE c2.c2_status = 1
GROUP BY c2.c2_id

Answer 1

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带有活动记录的查询

$select =   array('DISTINCT c2_id','f_id','f_name');
$this->db->select($select);
$this->db->from('file');
$this->db->order_by('f_id','DESC');
$subQuery1 = $this->db->_compile_select();

unset($select);

$this->db->_reset_select();

$select =   array('DISTINCT c2_id','f_id','f2_name');
$this->db->select($select);
$this->db->from('file2');
$this->db->order_by('f2_id','DESC');
$subQuery2 = $this->db->_compile_select();

unset($select); 

$this->db->_reset_select();

// And now your main query

$select =   array(
                  'c1.c1_id',
                  'c1.c1_name',
                  'c2.c2_id',
                  'c2.c2_name',
                  'c2.c2_type',
                  'c2.c2_status',
                  'f.f_id',
                  'f.f_name',
                  'f2.f2_id',
                  'f2.f2_name'
            );

$this->db->select($select);
$this->db->from('category2 c2');
$this->db->join("($subQuery1)",'f.c2_id = c2.c2_id','left');
$this->db->join("($subQuery2)",'f2.c2_id = c2.c2_id','left');
$this->db->where('c2.c2_status',1);
$this->db->group_by('c2.c2_id');
$main_query = $this->db->get();

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')

而不是

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

运行查询。

现在，您可以检查已构建为

的查询

echo $this->db->last_query();

Answer 2

$query='SELECT c1.c1_id, c1.c1_name, c2.c2_id, c2.c2_name, c2.c2_type, c2.c2_status, f.f_id, f.f_name, f2.f2_id, f2.f2_name FROM category2 c2 
LEFT JOIN category1 c1 ON c1.c1_id = c2.c1_id 
LEFT JOIN (
    SELECT DISTINCT c2_id, f_id, f_name FROM file ORDER BY f_id DESC
) f ON f.c2_id = c2.c2_id
LEFT JOIN (
    SELECT DISTINCT c2_id, f2_id, f2_name FROM file2 ORDER BY f2_id DESC
) f2 ON f2.c2_id = c2.c2_id
WHERE c2.c2_status = ?
GROUP BY c2.c2_id';
$params=array();
$params[]=1;
$result=$this->db->query($query,$params);
$result=$result->result_array();
print_r($result);

我会避免使用Codeigniter的Active Record类，除非你的目标是混淆你的代码。

“始终将代码视为最终维护代码的人是一个知道你住在哪里的暴力精神病患者。”

codeigniter mysql左连接包含select

2 个答案: