SQL to produce Top 10 and Other - sql

Question

Imagine I have a table showing the sales of Acme Widgets, and where they were sold. It's fairly easy to produce a report grouping sales by country. It's fairly easy to find the top 10. But what I'd like is to show the top 10, and then have a final row saying Other. E.g.,
Ctry | Sales
=============
GB | 100
US | 80
ES | 60
...
IT | 10
Other | 50
I've been searching for ages but can't seem to find any help which takes me beyond the standard top 10.
TIA

Answer 1

I tried some of the other solutions here, however they seem to be either slightly off, or the ordering wasn't quite right.
My attempt at a Microsoft SQL Server solution appears to work correctly:
SELECT Ctry, Sales FROM
(
SELECT TOP 2
Ctry,
SUM(Sales) AS Sales
FROM
Table1
GROUP BY
Ctry
ORDER BY
Sales DESC
) AS Q1
UNION ALL
SELECT
Ctry AS 'Other',
SUM(Sales) AS Sales
FROM
Table1
WHERE
Ctry NOT IN (SELECT TOP 2
Ctry
FROM
Table1
GROUP BY
Ctry
ORDER BY
SUM(Sales) DESC)
Note that in my example, I'm only using TOP 2 rather than TOP 10. This is simply due to my test data being rather more limited. You can easily substitute the 2 for a 10 in your own data.
Here's the SQL Script to create the table:
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
SET ANSI_PADDING ON
GO
CREATE TABLE [dbo].[Table1](
[Ctry] [varchar](50) NOT NULL,
[Sales] [float] NOT NULL
) ON [PRIMARY]
GO
SET ANSI_PADDING OFF
And my data looks like this:
GB 10
GB 21.2
GB 34
GB 16.75
US 10
US 11
US 56.43
FR 18.54
FR 98.58
WE 44.33
WE 11.54
WE 89.21
KR 10
PO 10
DE 10
Note that the query result is correctly ordered by the Sales value aggregate and not the alphabetic country code, and that the "Other" category is always last, even if it's Sales value aggregate would ordinarily push it to the top of the list.
I'm not saying this is the best (read: most optimal) solution, however, for the dataset that I provided it seems to work pretty well.

Answer 2

SELECT Ctry, sum(Sales) Sales
FROM (SELECT COALESCE(T2.Ctry, 'OTHER') Ctry, T1.Sales
FROM (SELECT Ctry, sum(Sales) Sales
FROM Table1
GROUP BY Ctry) T1
LEFT JOIN
(SELECT TOP 10 Ctry, sum(sales) Sales
FROM Table1
GROUP BY Ctry) T2
on T1.Ctry = T2.Ctry
) T
GROUP BY Ctry

Answer 3

The pure SQL solutions to this problem make multiple passes through the individual records more than once. The following solution only queries the data once, and uses a SQL ranking function, ROW_NUMBER() to determine if some results belong in the "Other" category. The ROW_NUMBER() function has been available in SQL Server since SQL Server 2008. In my database, this seems to have resulted in a more efficient query. Please note that the "Other" row will appear above some rows if the total of the "Other" sales exceeds the top 10. If this is not desired some adjustments would need to be made to this query:
SELECT CASE WHEN RowNumber > 10 THEN 'Other' ELSE Ctry END AS Ctry,
SUM(Sales) as Sales FROM
(
SELECT Ctry, SUM(Sales) as Sales,
ROW_NUMBER() OVER(ORDER BY SUM(Sales) DESC) AS RowNumber
FROM Table1 GROUP BY Ctry
) as AggregateQuery
GROUP BY CASE WHEN RowNumber > 10 THEN 'Other' ELSE Ctry END
ORDER BY SUM(Sales) DESC

Answer 4

Using a real analytics SQL engine, such as Apache Spark, you can use Common Table Expression with to do:
with t as (
select rank() over (order by sales desc) as r, sales,city
from DB
order by sales desc
)
select sales, city, r
from t where r <= 10
union
select sum(sales) as sales, "Other" as city, 11 as r
from t where r > 10

Answer 5

In pseudo SQL:
select top 10 order by sales
UNION
select 'Other',SUM(sales) where Ctry not in (select top 10 like above)

Answer 6

Union the top ten with an outer Join of the top ten with the table it self to aggregate the rest.
I don't have access to SQL here but I'll hazzard a guess:
select top (10) Ctry, sales from table1
union all
select 'other', sum(sales)
from table1
left outer join (select top (10) Ctry, sales from table1) as table2
on table2.Ctry = table2.Ctry
where table2.ctry = null
group by table1.Ctry
Of course if this is a rapidly changing top(10) then you either lock or maintain a copy of the top(10) for the duration of the query.

Answer 7

Have in mind that depending on your use (and database volume / restrictions) you can achieve the same results using application code (python, node, C#, java etc). Sure it will depend on your use-case but hey, it's possible.
I ended up doing this in C# for instance:
// Mockup Class that has a CATEGORY and it's VOLUME
class YourModel { string category; double volume; }
List<YourModel> groupedList = wholeList.Take (5).ToList ();
groupedList.Add (new YourModel()
{
category = "Others",
volume = tempChartData.Skip (5).Select (t => t.qtd).Sum ()
});
Disclaimer
I understand that this is a "SQL Only" tagged question, but there might be other people like me out there who can make use of the application layer instead of relying only on SQL to make it happen. I am just trying to show people other ways of doing the same thing, that might be helpful. Even if this gets downvoted to oblivion I know that someone will be happy to read this because they were taught to use each tool to it's best, and think "outside the box".