SQL Scalar function element not recognized in TSQL program

Question

I have an input db2 table with two elements: loan_number, debt_to_income; this table's name is #Input_Table. I am trying to run a test the function by running a SQL program against this table. The problem is that the function's element is not being recognized in the SQL program for some reason, maybe I have been looking at to long? I need to validate that the output in the table will output in a order by the debt_to_income field.

Here is the function code:

 ALTER FUNCTION [dbo].[FN_DTI_BANDS]
(
    -- the parameters for the function here
    @FN_DTI_Band            decimal(4,3)
     )
RETURNS varchar(16)
AS
BEGIN

declare @Return varchar(16)

select @Return =

        Case
        when @FN_DTI_Band is NULL then ' Missing'
        WHEN @FN_DTI_Band = 00.00 then ' Missing'
        When @FN_DTI_Band < = 0.31 then 'Invalid'
        When @FN_DTI_Band between 0.31 and 0.34 then '31-34'
        When @FN_DTI_Band between 0.34 and 0.38 then '34-38'
        When @FN_DTI_Band >= 0.38 then '38+'
        else null end
            -- Return the result of the function
            RETURN @Return
END

Here is the T-SQL test program:

SELECT  loan_number,dbo.FN_DTI_BANDS(debt_to_income)as FN_DTI_Band

from #Input_table

SELECT      COUNT(*), FN_DTI_Band
FROM  #Input_table
GROUP BY FN_DTI_Band
ORDER BY FN_DTI_Band

Here is the error:

Msg 207, Level 16, State 1, Line 7
Invalid column name 'FN_DTI_Band'.
Msg 207, Level 16, State 1, Line 5
Invalid column name 'FN_DTI_Band'.

Can someone help me spot what I am overlooking? Thank you!

Answer 1

Try prepending "dbo" onto the name of the function.

Select Count(*), dbo.FN_DTI_Band
From....

Answer 2

the table #input_table does not have a column called FN_DTI_Band.

Just the result of the first select statement has that column name.

You need to make the first select statement a sub query of the 2nd

Something like this:

SELECT COUNT(*), T.FN_DTI_Band
FROM 
(
   SELECT  loan_number,dbo.FN_DTI_BANDS(debt_to_income) as FN_DTI_Band
   from #Input_table
) T
GROUP BY T.FN_DTI_Band
ORDER BY T.FN_DTI_Band