如何使用 query() 方法获取 joined table 的数据

Question

如果我使用 query()，我在获取连接 table 的数据时遇到问题。我没有得到产品 table 的数据，如何在不使用 Active record 的情况下使用 query() 解决这个问题？这是我的数据库 table 结构

        category table
        +--------------------------+
        | cId | added  | category  |       
        +-----+--------+-----------+
        |  1  | 1.2.20 |  PC       |
        |  2  | 1.7.20 | electron  |
        +-----+--------+-----------+

        product table
        +--------------------------+
        | id  |  cId   |  cost     |       
        +-----+--------+-----------+
        |  1  |   1    |  3000     |
        |  1  |   2    |  9000     |
        +-----+--------+-----------+

我的模型

    protected $table = 'category';

    public function showProduct()
    {
        $sql = "SELECT 
                     category.*, COALESCE(SUM(product.cost),0) as price 
                FROM category 
                JOIN product 
                ON product.cId = category.cId
                GROUP BY category.cId
            ";
        $this->db->query($sql);
        return $this;
    }

我的控制器

    public function index()
    {
            $result = $this->model->showProduct();
            echo "<pre>";
            print_r($result->asObject()->paginate(1));  
            
            //pagination
            $pager = $this->model->showProduct()->pager->links();
    }

我得到的结果

    Array
    (
        [0] => stdClass Object
            (
                [cId] => 1
                [added] => 1.2.20
                [category] => PC
            )

        [1] => stdClass Object
            (
                [cId] => 2
                [added] => 1.7.20
                [category] => electron
            ),

    )

Answer 1

$sql="SELECT category*,product* FROM category INNER JOIN product.cid=category.id WHERE category.id";

Answer 2

您需要运行此代码。

SELECT category.cId,category.added,category.category,product.id,COALESCE(SUM(product.cost),0) as price
FROM category,product
WHERE category.cId=product.cId
GROUP BY category.cId;

如果您使用的是 CodeIgniter-4，那么您可以使用 Query Builder Class.

轻松编写此代码

Answer 3

我通过在函数中设置此 table 属性找到了解决方案。

型号

$protected $table = array("default bd table here");

public function showProduct()
{
    $this->table = array('category');
    
    $sql = "SELECT 
                 category.*, COALESCE(SUM(product.cost),0) as price 
            FROM category 
            JOIN product 
            ON product.cId = category.cId
            GROUP BY category.cId
        ";
    $this->db->query($sql);
    return $this;
}

我的控制器

public function index()
{
        $result = $this->model->showProduct();
        
        //pagination
        $pager = $this->model->showProduct()->pager->links();
}

如何使用 query() 方法获取 joined table 的数据

How to get data of joined table using query() method

mysql

codeigniter

codeigniter-4