SQL Transpose rows to columns (group by key variable) NOT using pivot - sql-server

Question

The following code is close to doing what I need EXCEPT I should generate columns (p1,p2,p3...) dynamically AND I can't use pivot (see SQL Transpose rows to columns (group by key variable)).
What I am using now in SQL Server 2008:
Select InvoiceNum,
Max(Case when seq =0 Then product_Description end) as p1,
Max(Case when seq =1 Then product_Description end) as p2
From
( Select InvoiceNum, Product_Description,
Row_Number() Over(Partition by InvoiceNum
Order by InvoiceNum) - 1 seq
From #tmpTable
)d
Group by InvoiceNum
Thank you StackOverFlow Community!!

Answer 1

I think, like the comments also say, you should use Dynamic SQL with a PIVOT table. It can probably be done more efficiently than this.
Create the table and put some data in it:
create table invoiceTable (
InvoiceNum int,
Product_Description nvarchar(20)
)
insert into invoiceTable values (1, 'inv1 row 1'),(1, 'inv1 row 2'),(1, 'inv1 row 3'),(2, 'inv2 row 1'),(2, 'inv2 row 2')
declare the necessary variables
declare #maxNo int
declare #query nvarchar(max)
declare #i int = 0
find the max row number:
select #maxNo = max(seq) from
(
Select
InvoiceNum
,Product_Description
,Row_Number() Over(Partition by InvoiceNum Order by InvoiceNum) - 1 seq
From
invoiceTable
) maxRowNo
Build the dynamic query
set #query =
'
Select
*
From
(
Select
InvoiceNum
,Product_Description
,Row_Number() Over(Partition by InvoiceNum Order by InvoiceNum) - 1 seq
From
invoiceTable
) d
pivot
(
min(Product_Description)
for seq in (
'
while (#i <= #maxNo)
begin
if (#i > 0) set #Query += ','
set #query += '['+CAST(#i as nvarchar)+']'
set #i += 1;
end
set #query +=
')
) pvt
'
Execute the query
exec sp_executesql #query
This gives the following resultset:
InvoiceNum 0 1 2
1 inv1 row 1 inv1 row 2 inv1 row 3
2 inv2 row 1 inv2 row 2 NULL