Question

我有两个表连接，其中一个表包含产品数据，其他定价数据包括多个折扣定价。并非每个产品在定价表中都有多个条目，因为有些产品只有一个单价。我想弄清楚的是在我的选择中如何设置一个标志，让我知道产品是否有多种定价。

我现在的代码（见下文）返回产品并找到每种产品的最低价格。但是我说并非所有产品都有“最低价”。我正在尝试确定产品的价格是单个单价还是最低价。

SELECT products.*
     , products_pricing.* 
  FROM products
  LEFT 
  JOIN products_pricing 
    ON products.product_id = products_pricing.product_id 
  LEFT 
  JOIN products_pricing AS filter 
    ON products_pricing.product_id = filter.product_id 
   AND products_pricing.qty_price > filter.qty_price 
 WHERE filter.product_id IS NULL 
   AND products.product_active > 0 
 ORDER 
    BY products.product_id DESC

Answer 1

根据您的描述，我收集到每个产品至少有products_pricing的价格，因此无需外部联接。

我只是加入聚合产品，而不是使用反连接模式。使用min / max或count的比较来获得你的旗帜。

select 
  p.*,
  pp.*,
  case when ppm.min_qty_price = ppm.max_qty_price then 'single' else 'multi' end as flag
from products p
join products_pricing pp on pp.product_id = p.product_id 
join 
(
  select product_id, min(qty_price) as min_qty_price, max(qty_price) as max_qty_price
  from products_pricing
  group by product_id
) ppm on ppm.product_id = pp.product_id
      and ppm.min_qty_price = pp.qty_price
where p.product_active > 0 
order by p.product_id desc;

Answer 2

如果您不需要两个表中的所有列，只需要相关的列

  SELECT products.product_id, count(*) as num_of_price
     , case when count(*) > 1 then 'MULTI PRICE' ELSE 'SINGLE PRICE' as flag_price
  FROM products
  LEFT 
  JOIN products_pricing 
    ON products.product_id = products_pricing.product_id 
 WHERE products.product_active > 0 
   GROUP BY products.product_id
 ORDER 
    BY products.product_id DESC

如果您需要所有列，则可以加入此结果

SELECT products.*
     , products_pricing.*
     , t.*
  FROM products
  LEFT JOIN products_pricing  ON products.product_id = products_pricing.product_id 
  LEFT JOIN (
      SELECT products.product_id, count(*) as num_of_price
         , case when count(*) > 1 then 'MULTI PRICE' ELSE 'SINGLE PRICE' as flag_price
      FROM products
      LEFT 
      JOIN products_pricing 
        ON products.product_id = products_pricing.product_id 
     WHERE products.product_active > 0 
       GROUP BY products.product_id
    ) T ON products.product_id = T.product_id
ORDER 
    BY products.product_id DESC

mysql join选择最低价格设置标志

2 个答案: