SQL，多行显示相同总计值的订单，如何计数一次？

Question

我有一个数据集，其中包含多行显示的唯一餐厅 ID 和订单，每个订单还有一列包含 Total_with_VAT

如果我像这样查询它，它会计算每行的总计，我如何修改它以仅计算唯一的订单 ID 以获得准确的总计？

SELECT DISTINCT Restaurant_ID,
  ROUND(SUM(Total__with_VAT_),2) AS Total_With_VAT
FROM rest.totals
GROUP BY Restaurant_ID
ORDER BY total_with_VAT DESC;

我尝试运行子查询，但它返回相同的结果

SELECT
  Restaurant_ID,
  ROUND(SUM(Total_with_VAT),2) AS Total_VAT
FROM (
  SELECT Restaurant_ID,
  SUM(Total__with_VAT_) AS Total_with_VAT
  FROM rest.totals
  GROUP BY Restaurant_ID
) AS subquery
GROUP BY Restaurant_ID
ORDER BY Total_VAT DESC;

Answer 1

您的数据是非规范化的，因为它在每一行上都有整个集合的总和。

需要按顺序分组得到

MIN

或

MAX

，然后再次分组求和。

SELECT
  rt.Restaurant_ID,
  ROUND(SUM(rt.Total_with_VAT), 2) AS Total_VAT
FROM (
    SELECT
      rt.Restaurant_ID,
      rt.Order_ID
      MIN(rt.Total__with_VAT_) AS Total_with_VAT
    FROM rest.totals rt
    GROUP BY
      rt.Restaurant_ID,
      rt.Order_ID
) AS rt
GROUP BY
  rt.Restaurant_ID
ORDER BY
  Total_VAT DESC;