Question

我的选择查询中有2个案例陈述： -

   case 
      when substr(tariff_name,1,1) = 'S' then 
        case 
          when t.utility = 'Water' then '107.96'
          when t.utility = 'Foam' then '104.96'
        end
      when substr(tariff_name,1,1) = 'J' then 
        case 
          when t.utility = 'Water' then '90.88'
          when t.utility = 'Foam' then '70.07'     
        end
   end AS Annual_SC_Cost, 
   case 
      when substr(tariff_name,1,1) = 'S' then 
        case 
          when t.utility = 'Water' then eac * 0.11821
          when t.utility = 'Foam' then eac * 0.02707
        end
      when substr(tariff_name,1,1) = 'J' then 
        case 
          when t.utility = 'Water' then eac * 0.1338
          when t.utility = 'Foam' then eac * 0.03055 
        end
   end AS Annual_Cons_Cost

我想做的是另一个基本上是这样的选择：

        case 
          when t.tlength = 12 then (Annual_SC_Cost * Annual_Cons_Cost) * 1
          when t.tlength = 24 then (Annual_SC_Cost * Annual_Cons_Cost) * 2
        end

这是否可行，如果没有，是否有另一种方法可以将计算保存到单个SQL查询中？

Answer 1

对于您展示的非常具体的计算，假设您只需要最终计算的结果（并且您不需要在第一个代码片段中创建的中间结果），您可以重新排列代码，以便每个计算都是做了一次。您甚至不需要别名来获得中间结果。像这样：

product

其他说明：var termsArray = []; var channelsArray = []; for (var i = 0; i < productData.length; i++) { for(var j = 0; j < productData[i].termsArr.length; j++){ termsArray.push(productData[i].termsArr[j]) } for(var k = 0; k < productData[i].channelsArr.length; k++){ channelsArray.push(productData[i].channelsArr[k]) } }相当于... , case <calculation that produces annual_sc_cost> end * case <calculation that produces annual_cons_cost> end * case t.length when 12 then 1 when 24 then 2 end，通常效率更高。此外，正如我在上面tariff_name like 'S%'演示的那样，您可以更简洁地编写substr(tariff_name, 1, 1,) = 'S'表达式，将某些内容与固定值进行比较。（阅读“简单”与“搜索”案例表达式 - 谷歌搜索这些短语;这个概念非常基本，不易理解和使用）。

Answer 2

也许是这样的：

   case 
      when substr(tariff_name,1,1) = 'S' then 
        case 
          when t.utility = 'Water' then '107.96'
          when t.utility = 'Foam' then '104.96'
        end
      when substr(tariff_name,1,1) = 'J' then 
        case 
          when t.utility = 'Water' then '90.88'
          when t.utility = 'Foam' then '70.07'     
        end
   end AS Annual_SC_Cost, 
   case 
      when substr(tariff_name,1,1) = 'S' then 
        case 
          when t.utility = 'Water' then eac * 0.11821
          when t.utility = 'Foam' then eac * 0.02707
        end
      when substr(tariff_name,1,1) = 'J' then 
        case 
          when t.utility = 'Water' then eac * 0.1338
          when t.utility = 'Foam' then eac * 0.03055 
        end
   end AS Annual_Cons_Cost

将第一个查询用作子字符串并再次加入表格。

Answer 3

您可以将查询用作内联视图，并对相应的别名字段执行操作，如下所示 -

SELECT CASE
          WHEN t.tlength = 12 THEN (Annual_SC_Cost * Annual_Cons_Cost) * 1
          WHEN t.tlength = 24 THEN (Annual_SC_Cost * Annual_Cons_Cost) * 2
       END final_output
  FROM (SELECT CASE
                  WHEN SUBSTR (tariff_name, 1, 1) = 'S'
                  THEN
                     CASE
                        WHEN t.utility = 'Water' THEN '107.96'
                        WHEN t.utility = 'Foam' THEN '104.96'
                     END
                  WHEN SUBSTR (tariff_name, 1, 1) = 'J'
                  THEN
                     CASE
                        WHEN t.utility = 'Water' THEN '90.88'
                        WHEN t.utility = 'Foam' THEN '70.07'
                     END
               END
                  AS Annual_SC_Cost,
               CASE
                  WHEN SUBSTR (tariff_name, 1, 1) = 'S'
                  THEN
                     CASE
                        WHEN t.utility = 'Water' THEN eac * 0.11821
                        WHEN t.utility = 'Foam' THEN eac * 0.02707
                     END
                  WHEN SUBSTR (tariff_name, 1, 1) = 'J'
                  THEN
                     CASE
                        WHEN t.utility = 'Water' THEN eac * 0.1338
                        WHEN t.utility = 'Foam' THEN eac * 0.03055
                     END
               END
                  AS Annual_Cons_Cost
          FROM t)

在计算字段中使用字段别名

3 个答案: