Question

I have a data table like this:

Group   ID    M0    M1    ...    M20
------------------------------------
    1    1    10    -2    ...     54
    1    2    -8    10    ...    -20
    2    6   -10    12    ...      0
    2    4    45    52    ...      0
    2    5    12   102    ...      0

I’m grouping my data by Group like so:

SELECT Group
     , round(sum(M0+M1+M2+...+M20)/count(ID),2) as profit
     , round(sum(M0),2) as M0
     , round(sum(M1),2) as M1
     , ...
     , round(sum(M20),2) as M20
FROM
    data_table
GROUP BY
    Group

What I need to add is IRR based on M0 to M20 columns.

I found an IRR function that looks like this:

CREATE FUNCTION [dbo].[ufn_IRR]
  (
   @strIDs VARCHAR(8000),
   @guess DECIMAL(30,10)
  )
RETURNS DECIMAL(30, 10)
AS 
  BEGIN
    DECLARE @t_IDs TABLE (
        id INT IDENTITY(0, 1),
        value DECIMAL(30, 10)
    )
    DECLARE @strID VARCHAR(12),@sepPos INT,@NPV DECIMAL(30, 10)
    SET @strIDs = COALESCE(@strIDs + ',', '')
    SET @sepPos = CHARINDEX(',', @strIDs)
    WHILE @sepPos > 0 
      BEGIN
        SET @strID = LEFT(@strIDs, @sepPos - 1)
        INSERT INTO @t_IDs ( value ) SELECT ( CAST(@strID AS DECIMAL(20, 10)) ) WHERE ISNUMERIC(@strID) = 1
        SET @strIDs = RIGHT(@strIDs, DATALENGTH(@strIDs) - @sepPos)
        SET @sepPos = CHARINDEX(',', @strIDs)
      END

    SET @guess = CASE WHEN ISNULL(@guess, 0) <= 0 THEN 0.00001 ELSE @guess END

    SELECT @NPV = SUM(value / POWER(1 + @guess, id)) FROM @t_IDs
    WHILE @NPV > 0 
      BEGIN
        SET @guess = @guess + 0.00001
        SELECT @NPV = SUM(value / POWER(1 + @guess, id)) FROM @t_IDs
      END
    RETURN @guess
  END

Sample usage looks like this:

SELECT  dbo.ufn_IRR('-4000,1200,1410,1875,1050',0.00001)

But in my case I would like to avoid creating string from my columns, as this:

 SELECT  dbo.ufn_IRR(
    cast(round(sum([M0]), 2) AS NVARCHAR)+','
   +cast(round(sum([M1]), 2) AS NVARCHAR)+','
   +cast(round(sum([M2]), 2) AS NVARCHAR)+','
   +cast(round(sum([M3]), 2) AS NVARCHAR)+','
   +cast(round(sum([M4]), 2) AS NVARCHAR)+','
   +...+','
   +cast(round(sum([M20]), 2) AS NVARCHAR)
 ,0.00001)

I think it is pointless to first create a string and then inside function cut it into table.
I would like to modify IRR function so than I can pass my columns, but I don’t have Idea how I should do that :/

Answer 1

CREATE FUNCTION [dbo].[ufn_IRR]
  (
   @s0 DECIMAL(30,10),
   @s1 DECIMAL(30,10),
   @s2 DECIMAL(30,10),
   @s3 DECIMAL(30,10),
   @s4 DECIMAL(30,10),
   @s5 DECIMAL(30,10),
   @s6 DECIMAL(30,10),
   @s7 DECIMAL(30,10),
   @s8 DECIMAL(30,10),
   @s9 DECIMAL(30,10),
   @s10 DECIMAL(30,10),
   @s11 DECIMAL(30,10),
   @s12 DECIMAL(30,10),
   @s13 DECIMAL(30,10),
   @s14 DECIMAL(30,10),
   @s15 DECIMAL(30,10),
   @s16 DECIMAL(30,10),
   @s17 DECIMAL(30,10),
   @s18 DECIMAL(30,10),
   @s19 DECIMAL(30,10),
   @s20 DECIMAL(30,10),
   @guess DECIMAL(30,10)
  )
RETURNS DECIMAL(30, 10)
AS 
  BEGIN
    DECLARE @t_IDs TABLE (
        id INT IDENTITY(0, 1),
        value DECIMAL(30, 10)
    )
    Declare @NPV DECIMAL(30, 10)

    INSERT INTO @t_IDs (value) values (@s0);
    INSERT INTO @t_IDs (value) values (@s1);
    INSERT INTO @t_IDs (value) values (@s2);
    INSERT INTO @t_IDs (value) values (@s3);
    INSERT INTO @t_IDs (value) values (@s4);
    INSERT INTO @t_IDs (value) values (@s5);
    INSERT INTO @t_IDs (value) values (@s6);
    INSERT INTO @t_IDs (value) values (@s7);
    INSERT INTO @t_IDs (value) values (@s8);
    INSERT INTO @t_IDs (value) values (@s9);
    INSERT INTO @t_IDs (value) values (@s10);
    INSERT INTO @t_IDs (value) values (@s11);
    INSERT INTO @t_IDs (value) values (@s12);
    INSERT INTO @t_IDs (value) values (@s13);
    INSERT INTO @t_IDs (value) values (@s14);
    INSERT INTO @t_IDs (value) values (@s15);
    INSERT INTO @t_IDs (value) values (@s16);
    INSERT INTO @t_IDs (value) values (@s17);
    INSERT INTO @t_IDs (value) values (@s18);
    INSERT INTO @t_IDs (value) values (@s19);
    INSERT INTO @t_IDs (value) values (@s20);

    SET @guess = CASE WHEN ISNULL(@guess, 0) <= 0 THEN 0.00001 ELSE @guess END

    SELECT @NPV = SUM(value / POWER(1 + @guess, id)) FROM @t_IDs
    WHILE @NPV > 0 
      BEGIN
        SET @guess = @guess + 0.00001
        SELECT @NPV = SUM(value / POWER(1 + @guess, id)) FROM @t_IDs
      END
    RETURN @guess
  END

And use it

dbo.ufn_IRR(round(sum([M0]), 2),
            round(sum([M1]), 2),
            .....
            round(sum([M20]),2),
            0.00001)