codeigniter 从多个表中选择最小和最大产品价格

Question

我需要从产品、价格中选择所有 (*) 行。但我需要从价格中选择 MIN 和 MAX 价格。我已经阅读了如何执行此操作，但是如何在 INNER JOIN 中执行此操作

这是我的 build_query() 函数：

 //build sql query string
public function build_query($type = "active")
{
    $select = "products.*,

        (SELECT CONCAT(price) FROM prices WHERE products.id = prices.product_id ORDER BY created_at DESC LIMIT 1) AS price;}

这是我的 products_maxmin_price() 函数：

public function get_shops_products_maxmin_price($parent_id)
{
    $this->build_query();
    $this->db->select('MAX(price) as p_max, MIN(price)  p_min ');
    $this->db->where('products.parent_id', clean_number($parent_id));
    return $this->db->get('products')->result();
}

这是我的观点：

<?php foreach ($shops_products_maxmin_price as $item): ?>
                         <?php echo $item->p_min; ?>
                        <?php endforeach; endif; ?>

<?php foreach ($shops_products_maxmin_price as $item): ?>
                         <?php echo $item->p_max; ?>
                        <?php endforeach; endif; ?>

Answer 1

试试下面这个查询：

SELECT MIN(`prices`.`price`) as `p_min`,
       MAX(`prices`.`price`) as `p_max`,
       `products`.*
FROM `prices`
JOIN `products`
ON `prices`.`product_id` = `products`.`id`
WHERE `products`.`parent_id` = `<PARENT_ID>`
GROUP BY `prices`.`product_id`;

我修改了这个问题的答案：MIN/MAX price for each product (query)

更新： 将查询转换为 Codeigniter 查询生成器，并将您的 2 函数合并为 1：

public function get_shops_products_maxmin_price($parent_id)
{
    $this->db->select_min('prices.price','p_min');
    $this->db->select_max('prices.price','p_max');
    $this->db->select('products.*');
    $this->db->join('products', 'prices.product_id = products.id');
    $this->db->where('products.parent_id', clean_number($parent_id));
    $this->db->order_by('prices.created_at','DESC');
    $this->db->group_by('prices.product_id');
    return $this->db->get('products')->result();
}