TSQL Select all columns without first n from function/procedure - sql

Question

I know this may sounds silly but I would like to create function that will process data from tables with different size.
Lets say I have first table like so:
ID IRR M0 M1
----------------------
1 0 -10 5
2 0 -20 10
3 0 -100 100
4 0 -10 0
And second table like so:
ID IRR M0 M1 M2
----------------------------
1 0 -10 5 60
2 0 -20 10 0
3 0 -100 100 400
4 0 -10 0 10
I would like to create function that will be able to process data from both tables.
I know that first column contains ID, second IRR, rest of columns will hold cash flow for specific month.
Function should be able to process all columns instead of first 2 and store result in second column.
I know that I can get all columns from specific table with:
SELECT COLUMN_NAME
FROM INFORMATION_SCHEMA.columns
WHERE TABLE_NAME = 'First_Table'
Problems begin when I would like to create function that will return those columns as rows.
I can create function like so:
CREATE FUNCTION UnpivotRow (#TableName varchar(50), #FromWhichColumn int, #Row int)
RETURNS #values TABLE
(
id INT IDENTITY(0, 1),
value DECIMAL(30, 10)
)
...
But how this function should look?
I think that ideal for this kind of processing table should look like so:
ProjectID TimePeriod Value
--------------------------------
1 0 -10
1 1 5
2 0 -20
2 1 10
3 0 -100
3 1 100
4 0 -10
4 1 0
I need to unpivot whole table without knowing number of columns.
EDIT:
If this can't be done inside function, then maybe inside a procedure?

Answer 1

This can be done using dynamic SQL to perform the UNPIVOT:
DECLARE #cols AS NVARCHAR(MAX),
#query AS NVARCHAR(MAX),
#colTP as NVARCHAR(MAX)
select #cols = stuff((select ','+quotename(C.name)
from sys.columns as C
where C.object_id = object_id('table1') and
C.name like 'M%'
for xml path('')), 1, 1, '')
set #query = 'SELECT id,
replace(timeperiod, ''M'', '''') timeperiod,
value
from table1
unpivot
(
value
for timeperiod in (' + #cols + ')
) u '
exec(#query)
See SQL Fiddle with Demo.
This solution would have to be placed in a stored procedure.