通过 CodeIgniter 中的 JOIN 和 GROUP BY 子句查询选择分组列值及其计数

Question

我有两张表如下：

- tblSaler

    SalerID  |  SalerName | 
    ----------------------|
    1        |  sothorn   |
    ----------------------|
    2        |  Daly      |  
    ----------------------|
    3        |  Lyhong    |
    ----------------------|
    4        | Chantra    |
    ----------------------|

- tblProduct

ProductID  | Product  | SalerID |
--------------------------------|
1          | Pen      | 3       |
--------------------------------|
2          | Book     | 2       |
--------------------------------|
3          | Phone    | 3       |
--------------------------------|
4          | Computer | 1       |
--------------------------------|
5          | Bag      | 3       |
--------------------------------|
6          | Watch    | 2       |
--------------------------------|
7          | Glasses  | 4       |
--------------------------------|

我需要的结果是：

sothorn | 1
Daly    | 2
Lyhong  | 3
Chantra | 1

我已经尝试过这个：

$this->db->select('count(SalerName) as sothorn where tblSaler.SalerID = 1, count(SalerName) as Daly where tblSaler.SalerID = 2, count(SalerName) as Lyhong where tblSaler.SalerID = 3, count(SalerName) as Chantra where tblSaler.SalerID = 4');
$this->db->from('tblSaler');
$this->db->join('tblProduct', 'tblSaler.SalerID = tblProduct.SalerID');

Answer 1

您可以使用此查询来实现此目的

SELECT
  tblSaler.SalerName,
  count(tblProduct.ProductID) as Total
FROM tblSaler
  LEFT JOIN tblProduct
    ON tblProduct.SalerID = tblSaler.SalerID
GROUP BY tblSaler.SalerID

这是此活动的记录

$select =   array(
                'tblSaler.SalerName',
                'count(tblProduct.ProductID) as Total'
            );  
$this->db
        ->select($select)
        ->from('tblSaler')
        ->join('tblProduct','Product.SalerID = tblSaler.SalerID','left')
        ->group_by('tblSaler.SalerID')
        ->get()
        ->result_array();

演示

输出

_____________________
| SALERNAME | TOTAL |
|-----------|-------|
|   sothorn |     1 |
|      Daly |     2 |
|    Lyhong |     3 |
|   Chantra |     1 |
_____________________           

Answer 2

请尝试此代码。它对我来说效果很好，对你也有帮助。

$this->db->select('SalerName, count(*)');
$this->db->from('tblSaler');        
$this->db->join('tblProduct', 'tblSaler.SalerID = tblProduct.SalerID'); 
$this->db->group_by('tblSaler.SalerID');       
$query = $this->db->get();

您可以使用下面的这一行获得完整的 SQL 查询

$query = $this->db->get(); 
echo $this->db->last_query();

Answer 3

试试这个

$this->db->select('SalerName, count(*)'); 
$this->db->from('tblSaler'); 
$this->db->join('tblProduct', 'tblSaler.SalerID = tblProduct.SalerID');
$this->db->group('SalerID');

Answer 4

$this->db->select($column_name);
$this->db->where($column_name, $type);
$q = $this->db->get($table_name);
$count = $q->result();
return count($count);