Use SQL function to get the original order number using the invoice number

Question

Hi All,
wondering is someone can help me with this challenge I am having?  Often I need to return the original order numbers that created the resulting invoce.  This is a relatively simple seriese of joins in a query but I am wanting to simplify it using a SQL function that can be referenced each time easily from with in the SELECT statement.  the code i currently have is:
Use SQL function to get the original order number using the invoice number
CREATE FUNCTION dbo.fnOrdersThatMakeInvoice(@InvNum int)
RETURNS nvarchar(200)
AS
BEGIN
DECLARE @OrderList nvarchar(200)
SET @OrderList = ''
SELECT @OrderList = @OrderList + (cast(T6.DocNum AS nvarchar(10)) + ' ')
FROM  OINV AS T1 INNER JOIN
      INV1 AS T2 ON T1.DocEntry = T2.DocEntry INNER JOIN
      DLN1 AS T4 ON T2.BaseEntry = T4.DocEntry AND T2.BaseLine = T4.LineNum INNER JOIN
      RDR1 AS T5 ON T4.BaseEntry = T5.DocEntry AND T4.BaseLine = T5.LineNum INNER JOIN
      ORDR AS T6 ON T5.DocEntry = T6.DocEntry
WHERE T1.DocNum = @InvNum
RETURN @OrderList 
END
it is run by the following query:
Select T1.DocNum, dbo.fnOrdersThatMakeInvoice(T1.DocNum)
From OINV T1
Where T1.DocNum = 'your invoice number here'
The issue is that this returns the order number for all of the lines in the invoice.  Only want to see the summary of the order numbers.  ie if 3 orders were used to make a 20 line inovice I only want to see the 3 order numbers retuned in the field.
If this was a simple reporting SELECT query I would use SELECT DISTINCT.  But I can't do that.
Any ideas?
Thanks,
Mike

Answer 1

Thanks Gordon,
I am trying to get away from the massive table access list everytime I write a query where I need to access the original order number of the invoice.  However, I have managed to solve my own problem with a GROUP BY statement!
Others may be interested so, the code is this:
CREATE FUNCTION dbo.fnOrdersThatMakeInvoice(@InvNum int)
RETURNS nvarchar(200)
AS
BEGIN
DECLARE @OrderList nvarchar(200)
SET @OrderList = ''
SELECT @OrderList = @OrderList + (cast(T6.DocNum AS nvarchar(10)) + ' ')
FROM  OINV AS T1 INNER JOIN
      INV1 AS T2 ON T1.DocEntry = T2.DocEntry INNER JOIN
      DLN1 AS T4 ON T2.BaseEntry = T4.DocEntry AND T2.BaseLine = T4.LineNum INNER JOIN
      RDR1 AS T5 ON T4.BaseEntry = T5.DocEntry AND T4.BaseLine = T5.LineNum INNER JOIN
      ORDR AS T6 ON T5.DocEntry = T6.DocEntry
WHERE T1.DocNum = @InvNum
GROUP BY T6.DocNum
RETURN @OrderList 
END
and to call it use this:
Select T1.DocNum, dbo.fnOrdersThatMakeInvoice(T1.DocNum)
From OINV T1
Where T1.DocNum = 'your invoice number'