sql - 展平查询结果

Question

我在创建 SQL 查询以整理我的记录时遇到了一些问题。我将展示这个例子会更容易

表看起来像这样

结果我想要这张桌子

任何人都可以帮助我吗？

Answer 1

您可以在使用过滤所需记录时尝试分组：case

  select ProductId,
         Sum(case 
               when MesurementType = 0 then Weight
               else 0
             end) "Weight calculated",
         Sum(case 
               when MesurementType = 1 then Weight
               else 0
             end) "Weight Weight measured"
    from MyTable
group by ProductId

Oracle 提供了Decode可以使查询更短的功能：

  select ProductId,
         Sum(Decode(MesurementType, 0, Weight, 0)) "Weight calculated",
         Sum(Decode(MesurementType, 1, Weight, 0))  "Weight Weight measured"
    from MyTable
group by ProductId

Answer 2

假设每个产品 ID 有 2 行，我们可以稍微修改一下上面的答案。

select ProductId,
     case 
           when MesurementType = 0 then Weight
           else 0
         end "Weight calculated",
      case 
           when MesurementType = 1 then Weight
           else 0
         end "Weight measured"
from MyTable

按产品 ID 分组

Answer 3

条件聚合绝对是要走的路。但是，如果测量类型只取1和0，您可以简单地使用算术：

select productid,
       sum(weight * (measurementtype - 1)) as weight_calculated,
       sum(weight * measurementtype) as weight_measured
from t
group by productid;