How to select info from row above? - sql

Question

I want to add a column to my table that is like the following:
This is just an example of how the table is structured, the real table is more than 10.000 rows.
No_ Name Account_Type Subgroup (New_Column)
100 Sales 3
200 Underwear 0 250 *100
300 Bikes 0 250 *100
400 Profit 3
500 Cash 0 450 *400
So for every time there is a value in 'Subgroup' I want the (New_Column) to get the value [No_] from the row above
No_ Name Account_Type Subgroup (New_Column)
100 Sales 3
150 TotalSales 3
200 Underwear 0 250 *150
300 Bikes 0 250 *150
400 Profit 3
500 Cash 0 450 *400
There are cases where the table is like the above, where two "Headers" are above. And in that case I also want the first above row (150) in this case.
Is this a case for a cursor or what do you recommend?
The data is ordered by No_
--EDIT--
Starting from the first line and then running through the whole table:
Is there a way I can store the value for [No_] where [Subgroup] is ''?
And following that insert this [No_] value in the (New_Column) in each row below having value in the [Subgroup] row.
And when the [Subgroup] row is empty the process will keep going, inserting the next [No_] value in (New_Column), that is if the next line has a value in [Subgroup]
Here is a better image for what I´m trying to do:

Answer 1

SQL Server 2012 suggests using Window Offset Functions.
In this case : LAG
Something like this:
SELECT [No_]
,[Name]
,[Account_Type]
,[Subgroup]
,LAG([No_]) OVER(PARTITION BY [Subgroup]
ORDER BY [No_]) as [PrevValue]
FROM table
Here is an example from MS:
http://technet.microsoft.com/en-us/library/hh231256.aspx

Answer 2

The ROW_NUMBER function will allow you to find out what number the row is, but because it is a windowed function, you will have to use a common table expression (CTE) to join the table with itself.
WITH cte AS
(
SELECT [No_], Name, Account_Type, Subgroup, [Row] = ROW_NUMBER() OVER (ORDER BY [No_])
FROM table
)
SELECT t1.*, t2.[No_]
FROM cte t1
LEFT JOIN cte t2 ON t1.Row = t2.Row - 1
Hope this helps.

Answer 3

Next query will return Name of the parent row instead of the row itself, i.e. Sales for both Sales, Underwear, Bikes; and Profit for Profit, Cash:
select ISNULL(t2.Name, t1.Name)
from table t1
left join table t2 on t1.NewColumn = t2.No

Answer 4

So in SQL Server 2008 i created test table with 3 values in it:
create table #ttable
(
id int primary key identity,
number int,
number_prev int
)
Go
Insert Into #ttable (number)
Output inserted.id
Values (10), (20), (30);
Insert in table, that does what you need (at least if understood correctly) looks like this:
declare #new_value int;
set #new_value = 13; -- NEW value
Insert Into #ttable (number, number_prev)
Values (#new_value,
(Select Max(number) From #ttable t Where t.number < #new_value))
[This part added] And to work with subgroup- just modify the inner select to filter out it:
Select Max(number) From #ttable t
Where t.number < #new_value And Subgroup != #Subgroup

Answer 5

SELECT
No_
, Name
, Account_Type
, Subgroup
, ( SELECT MAX(above.No_)
FROM TableX AS above
WHERE above.No_ < a.No_
AND above.Account_Type = 3
AND a.Account_Type <> 3
) AS NewColumn
FROM
TableX AS a