Codeigniter Active Record 中的子查询

Posted 2023-05-08

【中文标题】Codeigniter Active Record 中的子查询

【英文标题】：Sub-queries in Code Igniter Active Records

【发布时间】：2016-03-15 19:52:10

【问题描述】：

我正在尝试在 CI Active Records 中编写以下 mysql 查询。该查询使用子查询，但我正在努力解决这个问题。

有问题的查询：

SELECT 
                COUNT(*) AS no_skus, 
                pd_vendor AS brand, 
                (SELECT COUNT(DISTINCT(pd_model_code)) 
                FROM product_data
                WHERE pd_vendor = PD.pd_vendor ) AS unique_models
                FROM product_data PD
                GROUP BY pd_vendor
                ORDER BY 
                COUNT(*) DESC";

谁能建议如何将其编写/构造为 CI 活动记录。谢谢

【问题讨论】：

参考：arjunphp.com/… 和 ***.com/questions/6047149/…

谢谢，第一个链接让我设法创建了查询

【参考方案1】：

检查一下：

SELECT COUNT(*) AS no_skus, 
        pd_vendor AS brand, 
        (SELECT COUNT(DISTINCTpd_model_code) FROM product_data WHERE pd_vendor = PD.pd_vendor ) AS unique_models
FROM product_data 
GROUP BY pd_vendor
ORDER BY no_skus DESC;

【参考方案2】：

在 Codeigniter 方式中，您可以像这样编写此子查询

function getProductData()
$this->db->select("COUNT(*) AS no_skus,pd_vendor AS brand,(SELECT COUNT(DISTINCT(pd_model_code)) FROM product_data
                WHERE pd_vendor = PD.pd_vendor ) AS unique_models",false);// second parameter for escape--we disable to escap as codeigniter adding ` to protect identifiers
            $this->db->from("product_data PD");
            $this->db->group_by('pd_vendor');
            $this->db->order_by('no_skus', 'DESC');
            $result_arr=$this->db->get()->result_array();
return $result_arr

【参考方案3】：

我设法让这个工作，诚然使用相当松散类型的 Active Record 语法。代码在这里：

// Main Query
$this->db->select('
        COUNT(*) AS no_skus,
        pd_vendor AS brand')
        ->from('product_data PD')
        ->group_by('pd_vendor');

// Sub Query
$this->db->select('(SELECT
        COUNT(DISTINCT(pd_model_code)) 
        FROM product_data
        WHERE pd_vendor = PD.pd_vendor ) 
        AS unique_models');
$subQuery = $this->db->last_query();

$query = $this->db->get();
return $query->result();