php - mysql查询错误opencart过滤价格

Question

我正在为 opencart 2.0 创建过滤器模块 这是我的代码:
模型/目录/product.php
函数 getProducts()

................................... SOME CODES.............
            //Filter products based on slider price range

            if ((isset($this->request->get['lower']))&&(isset($this->request->get['higher'])))
            {
            $sql .=  " AND p.price >='". $this->request->get['lower'] ." ' AND p.price <='". $this->request->get['higher'] ."'" ;
            }

            //Filter products based on price slider

        if (!empty($data['filter_manufacturer_id'])) {
            $sql .= " AND p.manufacturer_id = '" . (int)$data['filter_manufacturer_id'] . "'";
        }

这对于没有特殊功能的产品非常有用。 但我正在尝试将此代码用于特殊用途。 所以我将我的 SQL 查询更改为:

    if ((isset($this->request->get['lower']))&&(isset($this->request->get['higher'])))
    {
    $sql .=  " AND (CASE WHEN special IS NOT NULL THEN special WHEN discount IS NOT NULL THEN discount ELSE p.price END) >='". $this->request->get['lower'] ." ' AND (CASE WHEN special IS NOT NULL THEN special WHEN discount IS NOT NULL THEN discount ELSE p.price END) <='". $this->request->get['higher'] ."'" ;
    }

但它不适用于具有特殊性的产品。

我收到此错误:“where 子句”中的未知列“special”

Answer 1

在sql的WHERE语句前添加如下内容

LEFT JOIN " . DB_PREFIX . "product_special p2s ON p.product_id = ps.product_id LEFT JOIN " . DB_PREFIX . "product_discount p2d ON p.product_id = pt.product_id

然后在 sql 上使用 'special' 作为 'p2s.special' 和 'discount' 作为 'p2d.discount'