Question

我有一个运输计算器的查询，该计算器应该根据几个标准（如重量和国家/地区）从数据库中选择最低值。该查询旨在获得符合条件的一个或多个ShippingProviderIds的第一个最低值。

问题是group by query混合了来自ShippingCost表的几行的结果，并将hings抛出了whack。我需要Price和ShippingCostId来自同一行。如何防止混合结果？也许Group By不是我需要的？

SELECT MIN(s1.Price), s1.ShippingCostId, s1.Weight, s2.CoD, s2.Artnr, s2.CoD, 
s2.Regular, s2.ShippingProviderId, s3.ProviderName FROM ShippingCost s1

INNER JOIN ShippingProvider s2 ON s1.ShippingProviderId = s2.ShippingProviderId 
INNER JOIN ShippingProviderTranslations s3 ON (s2.ShippingProviderId = s3.ShippingProviderId AND s3.Language = 'xx') 

WHERE CountryId = 123 AND (Weight >= 0.5 AND Weight <= 50) AND s2.Regular = 0

GROUP BY s2.ShippingProviderId

如果我删除了MIN（）表达式，则行不会再混合，但最低值不是找到的值，因为它具有较高的值，它具有较高的ShippingCostId并且稍后被添加（是主键）。无法为重量添加MIN（）表达式，或尝试按重量排序。我尝试了很多不同的方法，但我感到难过。

有什么建议吗？

Answer 1

您支持使用最低价格的连接而不是未按列分组的选择

SELECT t1.min_price, s1.ShippingCostId, s1.Weight, s2.CoD, s2.Artnr, s2.CoD, 
s2.Regular, s2.ShippingProviderId, s3.ProviderName 

FROM ShippingCost s1

INNER JOIN ShippingProvider s2 ON s1.ShippingProviderId = s2.ShippingProviderId 
INNER JOIN ShippingProviderTranslations s3 ON (s2.ShippingProviderId = s3.ShippingProviderId AND s3.Language = 'xx') 
INNER JOIN (
  select MIN(s1.Price) as min_price, s2.ShippingProviderId
  from FROM ShippingCost s1 
  INNER JOIN ShippingProvider s2 ON s1.ShippingProviderId = s2.ShippingProviderId 
  group by s2.ShippingProviderId
) t1 on t1.ShippingProviderId = s2.ShippingProviderId and s1.Price= t1.min_price

使用select而不是具有聚合功能的列的gruoped会产生不可预测的结果
这种习惯在SQL中被弃用，在最新版本的mysql中不允许并产生错误

使用GROUP BY时防止混合行？

1 个答案: