SQL Loop to build Case based on Variables - sql

Question

I am trying to build a case query based on variables
The idea being is when the variables are populated the case statement would alter accordingly.
My Current query takes Values from a table and groups them together into a sort of Bucket.
This works fine providing its always going to be the set ranges and number of ranges, I want to make this configurable by passing variables
From my original query all i wanted was to configure the Number of Buckets and the value of From and Two for each bucket i.e. +5 or +10
Here is my original query:
SELECT subq.Bucket, COUNT(*) 'Count'
FROM
(
SELECT
CASE
WHEN R.Value < 10 THEN '0-10'
WHEN R.Value Between 10 and 20 THEN '10-20'
WHEN R.Value Between 20 and 30 THEN '20-30'
WHEN R.Value Between 30 and 40 THEN '30-40'
WHEN R.Value > 40 THEN '40+'
END Bucket
FROM Table R
Where DateTime Between '2022-10-01' and '2022-11-10' and Type = 1
) subq
GROUP BY subq.Bucket
This is what i was trying to achomplish if it makes any sense in the realm of SQL
DECLARE #NoRows Int, #Range Int, #Count Int, #StartRange Int
Set #NoRows = 5
Set #StartRange = 0
Set #Range = 10
Set #Count = 0
SELECT subq.Bucket, COUNT(*) 'Count'
FROM
(
WHILE #NoRows <= #Count
BEGIN
SELECT
(
CASE
WHEN R.Value Between #StartRange and #Range THEN '#StartRange-#Range'
SET #Count = #Count + 1
SET #StartRange = #StartRange + #Range
END
WHEN R.Value > #StartRange THEN '#StartRange'
END Bucket
FROM Table R
Where DateTime Between '2022-10-01' and '2022-11-10' and Type = 1
) subq
GROUP BY subq.Bucket

Answer 1

This is untested, due to no sample data, but this should be enough to get you to where you need to be. I use an inline tally here to generate the data, but you could also use a tally function, or even build you own bucket function:
DECLARE #NoRows int = 5,
#Range int = 10,
#StartRange int = 0;
WITH N AS(
SELECT N
FROM (VALUES(NULL),(NULL),(NULL),(NULL),(NULL),(NULL),(NULL),(NULL),(NULL))N(N)),
Tally AS(
SELECT TOP(#NoRows)
ROW_NUMBER() OVER (ORDER BY (SELECT NULL)) AS I
FROM N N1, N N2), --UP to 100 rows, add more cross joins for more rows
Buckets AS(
SELECT #StartRange + ((I-1)*#Range) AS RangeStart,
#StartRange + ((I)*#Range) AS RangeEnd
FROM Tally)
SELECT YT.{Needed Columns},
CASE WHEN B.RangeStart IS NULL THEN CONCAT(#NoRows * #Range,'+')
ELSE CONCAT(B.RangeStart,'-', B.RangeEnd-1)
END AS Bucket
FROM dbo.YourTable YT
LEFT JOIN Buckets B ON YT.YourColumn >= B.RangeStart
AND YT.YourColumn < B.RangeEnd;
In SQL Server 2022+, you even have the built in function GENERATE_SERIES, which makes this even easier.