Assign rownumber in SQL grouped on value and n rows per rownumber - sql

Question

I am trying to generate a report with 3 rows per page for each order number using the following SQL.
As you can see from the results the fields Actual & Expected do not match up.
Any help would be appreciated.
set nocount on
DECLARE #Orders TABLE (Expected int, OrderNumber INT, OrderDetailsNumber int)
Insert into #orders values (0,1,1)
Insert into #orders values (0,1,2)
Insert into #orders values (0,1,3)
Insert into #orders values (1,1,4)
Insert into #orders values (2,2,5)
Insert into #orders values (2,2,6)
Insert into #orders values (2,2,7)
Insert into #orders values (3,2,8)
Insert into #orders values (3,2,9)
select cast(((row_number() over( order by OrderNumber)) -1) /3 as int) as [Actual]
,*
from #orders
Actual Expected OrderNumber OrderDetailsNumber
----------- ----------- ----------- ------------------
0 0 1 1
0 0 1 2
0 0 1 3
1 1 1 4
1 2 2 5
1 2 2 6
2 2 2 7
2 3 2 8
2 3 2 9

Answer 1

Right, after a couple of edits I have the final answer:
SELECT DENSE_RANK() OVER (Order BY OrderNumber, floor(RowNumber/3)) - 1 AS Actual,
Expected,
OrderNumber,
OrderDetailsNumber
FROM
(
SELECT *,
ROW_NUMBER() OVER (
PARTITION BY OrderNumber
ORDER BY OrderDetailsNumber
) - 1 AS RowNumber
FROM #Orders
) RowNumberTable
Gives the result (with extra rows for testing):
Actual Expected OrderNumber OrderDetailsNumber
-------------------- ----------- ----------- ------------------
0 0 1 1
0 0 1 2
0 0 1 3
1 1 1 4
1 1 1 12
2 2 2 5
2 2 2 6
2 2 2 7
3 3 2 8
3 3 2 9
3 4 2 11
4 3 2 27
5 5 3 10
This only works where OrderDetailsNumber is unique such that the result is deterministic.
Edit
I've now got the complete code working, however the dependence on OrderDetailsNumber being in order is very iffy, hopefully you can test and edit as required.
Edit 2
I've put the 'golfed' version in the main answer.
WITH FirstCTE AS
(
SELECT
OrderNumber,
OrderDetailsNumber,
Expected,
ROW_NUMBER() OVER (
PARTITION BY OrderNumber
ORDER BY OrderDetailsNumber
) - 1 AS RowNumber
FROM #Orders
)
, SecondCTE AS
(
SELECT OrderDetailsNumber as odn,
floor(RowNumber/3) as page_for_order_number,
DENSE_RANK() OVER (Order BY OrderNumber, floor(RowNumber/3)) - 1 AS Actual
FROM FirstCTE
)
SELECT c2.page_for_order_number,
c1.RowNumber,
C2.Actual,
c1.Expected,
c1.OrderNumber,
c1.OrderDetailsNumber
FROM FirstCTE AS c1
INNER JOIN SecondCTE AS c2
on c2.odn = c1.OrderDetailsNumber

Answer 2

This strikes me as a bit of a hack, but it works...
Divide the row_number() by 3, and use CEILINGto get the smallest integer greater than or equal to the result of that division.
select row_number() over( order by OrderNumber) as [Actual],
cast (row_number() over(order by ordernumber) as decimal(5,1)) / 3,
CEILING(cast (row_number() over(order by ordernumber) as decimal(5,1)) / 3)as GRPR,
*
from #orders
EDIT: Dang it, can never get results to line up. The 3rd column in the result set is your "page number".
Which yields:
Actual (No column name) PG_NBR Expected OrderNumber OrderDetailsNumber
1 0.333333 1 0 1 1
2 0.666666 1 0 1 2
3 1.000000 1 0 1 3
4 1.333333 2 1 1 4
5 1.666666 2 2 2 5
6 2.000000 2 2 2 6
7 2.333333 3 2 2 7
8 2.666666 3 3 2 8
9 3.000000 3 3 2 9