php - MYSQL 查询到 Codeigniter 查询

Question

当我在 phpMyAdmin 中使用它时，下面的查询工作正常，我只是有点不确定当我拥有 m.id 等时如何在 CI 框架中执行它。

查询:

SELECT DISTINCT m.name, m.id, c.id, c.name
FROM  `default_ps_products` p
INNER JOIN  `default_ps_products_manufacturers` m ON p.manufacturer_id = m.id
INNER JOIN  `default_ps_product_x_cats` x ON p.id = x.product_id
INNER JOIN  `default_ps_products_categories` c ON x.category_id = c.id

Answer 1

方法有很多。

示例1:

$result = $this->db
    ->select('m.name, m.id, c.id, c.name')
    ->distinct()
    ->join('default_ps_products_manufacturers m', 'p.manufacturer_id=m.id')
    ->join('default_ps_product_x_cats x', 'p.id=x.product_id')
    ->join('default_ps_products_categories c', 'x.category_id=c.id')
    ->get('default_ps_products p')
    ->result();

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

有时事件记录无法生成您想要的查询。所以你可以自己写。

示例2:

$query = "SELECT DISTINCT m.name, m.id, c.id, c.name
           FROM  `default_ps_products` p
           INNER JOIN  `default_ps_products_manufacturers` m ON p.manufacturer_id = m.id
           INNER JOIN  `default_ps_product_x_cats` x ON p.id = x.product_id
           INNER JOIN  `default_ps_products_categories` c ON x.category_id = c.id";

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

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

在第二个示例中，db::query() 可以采用数组作为第二个参数，该参数将用相应的值替换 $query 中的任何问号 (?)。例如，假设您需要向查询添加一些 where 值。

示例3:

$query = "SELECT DISTINCT m.name, m.id, c.id, c.name
          FROM  `default_ps_products` p
          INNER JOIN  `default_ps_products_manufacturers` m ON p.manufacturer_id = m.id
          INNER JOIN  `default_ps_product_x_cats` x ON p.id = x.product_id
          INNER JOIN  `default_ps_products_categories` c ON x.category_id = c.id
          WHERE c.id=?";

$result = $this->db
    ->query($query, array(1))
    ->result();

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