Custom Query Output Ordering with a CASE function - sql-server

Question

I often find when I am pulling data for analysis, that I group the number of orders a customer has placed into ranges, such as:
1-2
3-5
6-9
10-12
13-15
I do this with a CASE function. However, when you get the query results, the order ranges will be listed like:
1-2
10-12
13-15
3-5
6-9
This easy to correct in Excel when you have 1 query and a few order range groups. However, when you're pulling many queries, it's a pain to correct this over and over.
What is the best way to pull a range and have it ordered correctly?
here's an example of the query I would write:
SELECT
OrderRange = CASE
WHEN COUNT(OrderID) BETWEEN 1 AND 5 THEN '1-5'
WHEN COUNT(OrderID) BETWEEN 6 AND 10 THEN '6-10'
WHEN COUNT(OrderID) > 10 THEN '10+'
ELSE 'Error'
END
FROM Orders
GROUP BY CASE
WHEN COUNT(OrderID) BETWEEN 1 AND 5 THEN '1-5'
WHEN COUNT(OrderID) BETWEEN 6 AND 10 THEN '6-10'
WHEN COUNT(OrderID) > 10 THEN '10+'
ELSE 'Error'
END
ORDER BY... ?

Answer 1

I'd keep a table of ranges, e.g. (indices not written)
CREATE TABLE Ranges (RangeSet int, MinVal int, MaxVal int, Name varchar(50));
and then e.g.
INSERT INTO ranges VALUES
(1,1,5,'1-5'),(1,6,10,'6-10'),(1,11,-1,'11+'),
(2,1,10,'1-10'),(2,11,20,'11-20'),(2,21,30,'21-30'),(2,31,-1,'31+');
you get the idea. Now you do something like (table and field names free fiction)
SELECT
CustomerID,
count(OrderID) AS OrderCount
FROM Orders
WHERE <whatever, e.g order_date BETWEEN ... AND ...>
GROUP BY CustomerID
HAVING OrderCount>0
as you'd normally would expect, but wrap it in a superquery joining to the Ranges table
SELECT
BaseView.CustomerID as CustomerID,
Ranges.Name as OrderRange
FROM (
SELECT
CustomerID,
count(OrderID) AS OrderCount
FROM Orders
WHERE <whatever, e.g order_date BETWEEN ... AND ...>
GROUP BY CustomerID
HAVING OrderCount>0
) AS BaseView
INNER JOIN Ranges ON
Ranges.RangeSet=<id-of-required-rangeset>
AND BaseView.OrderCount>=Ranges.MinVal
AND (BaseView.OrderCount<=Ranges.MaxVal OR Ranges.MaxVal=-1)
ORDER BY RangeSet.MinVal DESC
;
Now you just have to supply the RangeSet you want to apply, maybe creating a new one on occasion.
Disclaimer: This is a performance-killer

Answer 2

If I'm understanding you correctly you want the list of customers and order ranges ordered from least to highest. You should be able to do that by just ordering by the count(orderID)
SELECT CustomerID,
OrderRange = CASE
WHEN COUNT(OrderID) BETWEEN 1 AND 5 THEN '1-5'
WHEN COUNT(OrderID) BETWEEN 6 AND 10 THEN '6-10'
WHEN COUNT(OrderID) > 10 THEN '10+'
ELSE 'Error'
END ,
FROM Orders
GROUP BY CustomerID
order by count(orderid)
Results:
CustomerId OrderRange
CENTC 1-5
GROSR 1-5
LAZYK 1-5
...
ROMEY 1-5
VINET 1-5
ALFKI 6-10
CACTU 6-10
...
VICTE 6-10
WANDK 6-10
BLONP 10+
GREAL 10+
RICAR 10+
...
QUICK 10+
ERNSH 10+
SAVEA 10+