Question

Imagine this case, but with a lot more component buckets and a lot more intermediates and outputs. Many of the intermediates are calculated at the detail level, but a few things are calculated at the aggregate level:

DECLARE @Profitability AS TABLE
    (
     Cust INT NOT NULL
    ,Category VARCHAR(10) NOT NULL
    ,Income DECIMAL(10, 2) NOT NULL
    ,Expense DECIMAL(10, 2) NOT NULL
    ,Liability DECIMAL(10, 2) NOT NULL
    ,AllocatedCapital DECIMAL(10, 2) NOT NULL
    ) ;

INSERT  INTO @Profitability
VALUES  ( 1, 'Software', 100, 50, 0, 0 ) ; 
INSERT  INTO @Profitability
VALUES  ( 2, 'Software', 100, 20, 0, 0 ) ; 
INSERT  INTO @Profitability
VALUES  ( 3, 'Software', 100, 60, 0, 0 ) ; 
INSERT  INTO @Profitability
VALUES  ( 4, 'Software', 500, 400, 0, 0 ) ; 
INSERT  INTO @Profitability
VALUES  (
         5
        ,'Hardware'
        ,1000
        ,550
        ,0
        ,0 
        ) ; 
INSERT  INTO @Profitability
VALUES  (
         6
        ,'Hardware'
        ,1000
        ,250
        ,500
        ,200 
        ) ; 
INSERT  INTO @Profitability
VALUES  (
         7
        ,'Hardware'
        ,1000
        ,700
        ,500
        ,600 
        ) ; 
INSERT  INTO @Profitability
VALUES  (
         8
        ,'Hardware'
        ,5000
        ,4500
        ,2500
        ,800 
        ) ; 

WITH    ProfitView
          AS ( SELECT   Cust
                       ,Category
                       ,Income
                       ,Expense
                       ,Profit = Income - Expense
                       ,NetProfit = Income - Expense
                        - CASE WHEN Liability - AllocatedCapital > 0
                               THEN Liability - AllocatedCapital
                               ELSE 0
                          END
               FROM     @Profitability
             )
    SELECT  Cust
           ,Category
           ,Income
           ,Expense
           ,Profit
           ,NetProfit
           ,Margin = Profit / Income
           ,NetMargin = NetProfit / Income
    FROM    ProfitView ; -- NOTE I've left off the AFTER grouping formulas on this one.

WITH    ProfitView
          AS ( SELECT   Cust
                       ,Category
                       ,Income
                       ,Expense
                       ,Profit = Income - Expense
                       ,NetProfit = Income - Expense
                        - CASE WHEN Liability - AllocatedCapital > 0
                               THEN Liability - AllocatedCapital
                               ELSE 0
                          END
               FROM     @Profitability
             ),
        GROUP1
          AS ( SELECT   Category
                       ,SUM(Profit) AS Profit
                       ,SUM(NetProfit) AS NetProfit
                       ,SUM(Income) AS Income
                       ,SUM(Profit) / SUM(Income) AS Margin
                       ,SUM(NetProfit) / SUM(Income) AS NetMargin
               FROM     ProfitView
               GROUP BY Category
             ),
        GROUP2
          AS ( SELECT   GROUP1.*
                       ,NetProfit - Profit AS Exposure
               FROM     GROUP1
             )
    SELECT  *
           ,Exposure / Income AS ExposureRatio
    FROM    GROUP2 ;

WITH    ProfitView
          AS ( SELECT   Cust
                       ,Category
                       ,Income
                       ,Expense
                       ,Profit = Income - Expense
                       ,NetProfit = Income - Expense
                        - CASE WHEN Liability - AllocatedCapital > 0
                               THEN Liability - AllocatedCapital
                               ELSE 0
                          END
               FROM     @Profitability
             ),
        GROUP1
          AS ( SELECT   SUM(Profit) AS Profit
                       ,SUM(NetProfit) AS NetProfit
                       ,SUM(Income) AS Income
                       ,SUM(Profit) / SUM(Income) AS Margin
                       ,SUM(NetProfit) / SUM(Income) AS NetMargin
               FROM     ProfitView
             ),
        GROUP2
          AS ( SELECT   GROUP1.*
                       ,NetProfit - Profit AS Exposure
               FROM     GROUP1
             )
    SELECT  *
           ,Exposure / Income AS ExposureRatio
    FROM    GROUP2 ;

Notice how the same formulae have to be used at the different aggregation levels. This results in code duplication.

I have thought of using UDFs (either scalar or table valued with an OUTER APPLY, since many of the final results may share intermediates which have to be calculated at the aggregate level), but in my experience the scalar and multi-statement table-valued UDFs perform very poorly.

Also thought about using more dynamic SQL and applying the formulas by name, basically.

Any other tricks, techniques or tactics to keeping these kinds of formulae which need to be applied at different levels in sync and/or organized?

Answer 1

Notice how the same formulae have to be used at the different aggregation levels. This results in code duplication.

If you functions were more complex, you could benefit from creating a custom CLR aggregate.

However, for such a simple function, a built-in SUM is the best.

Unlike PostgreSQL, SQL Server does not allow creating custom aggregates in a built-in language.