Question

It would be easier to explain with an example. Suppose I wanted to get at most 5 items per group.

My input would be a table looking like this:

Item    Count
A        2
A        3
A        3
B        4
B        4
B        5
C        1

And my desired output would look like this:

Item     Count
A        5
A>5      3
B        4
B>5      9
C        1

An alternative output that I could also work with would be

Item    Count    RunningTotal
A       2        2
A       3        5
A       3        8
B       4        4
B       4        8
B       5        13
C       1        1

I can use ROW_NUMBER() to get the top X records in each group, however my requirement is to get the top X items for each group, not X records. My mind is drawing a blank as to how to do this.

Answer 1

declare @yourTable table (item char(1), [count] int)

insert into @yourTable
select 'A', 2 union all
select 'A', 3 union all
select 'A', 3 union all
select 'B', 4 union all
select 'B', 4 union all
select 'B', 5 union all
select 'C', 1

;with cte(item, count, row) as (
    select *, row_number() over ( partition by item order by item, [count]) 
    from @yourTable
)
select t1.Item, t1.Count, sum(t2.count) as RunningTotal from cte t1
join cte t2 on t1.item = t2.item and t2.row <= t1.row
group by t1.item, t1.count, t1.row

Result:

Item Count       RunningTotal
---- ----------- ------------
A    2           2
A    3           5
A    3           8
B    4           4
B    4           8
B    5           13
C    1           1