Select top 5 and bottom 5 columns from a list of columns based on their values - tsql

Question

I have a requirement where I need to Select top 5 and bottom 5 columns from a list of columns based on their values.
If more than 1 column has same value then select any one from them.
Eg
CREATE TABLE #b(Company VARCHAR(10),A1 INt,A2 INt,A3 INt,A4 INt,B1 INt,G1 INt,G2 INt,G3 INt,HH5 INt,SS6 INt)
INSERT INTo #b
SELECT 'test_A',8,10,6,10,0,6,0,6,13,4 UNION ALL
SELECT 'test_B',17,7,0,1,3,18,0,6,9,5 UNION ALL
SELECT 'test_C',0,0,6,1,2,6,3,4,3,2 UNION ALL
SELECt 'test_D',13,1,4,1,4,1,9,0,0,5
SELECT * FROM #b
Desired Output:
Company
Top5
Bottom5
test_A
HH5,A2,A1,A3,SS6
B1,SS6,A3,A1,A2
test_B
G1,A1,HH5,A2,G3
A3,A4,B1,SS6,G3
I am able to find the top values but not the column names.
Here is I am stuck at, I am able to find the max scores but not sure how to find the column that holds this max value.
SELECT Company,(
SELECT MAX(myval)
FROM (VALUES (A1),(A2),(A3),(A4),(B1),(G1),(G2),(G3),(HH5)) AS temp(myval))
AS MaxOfColumns
FROM #b

Answer 1

As Larnu suggested, the first step would be to UNPIVOT the data into a form like (Company, ColumnName, Value). You can then use the ROW_NUMBER() window function to assign ordinals 1 - 10 to each value for each company based on the sorted value.
Next, you can wrap the above in a Common Table Expression (CTE) to feed a query that, for each Company, uses conditional aggregation with the STRING_AGG() to selectively combine the top 5 and bottom 5 column names to produce the desired result.
Something like:
;WITH Data AS (
SELECT
Company,
ColumnName,
Value,
ROW_NUMBER() OVER(PARTITION BY Company ORDER BY Value DESC, ColumnName) AS Ord
FROM #b
UNPIVOT (
Value FOR ColumnName IN (A1, A2, A3, A4, B1, G1, G2, G3, HH5, SS6)
) U
)
SELECT
D.Company,
STRING_AGG(CASE WHEN D.Ord BETWEEN 1 AND 5 THEN D.ColumnName END, ', ')
WITHIN GROUP (ORDER BY D.ORD) AS Top5,
STRING_AGG(CASE WHEN D.Ord BETWEEN 6 AND 10 THEN D.ColumnName END, ', ')
WITHIN GROUP (ORDER BY D.ORD) AS Bottom5
FROM Data D
GROUP BY D.Company
ORDER BY D.Company
For older SQL Server versions that don't support STRING_AGG(), the FOR XML PATH(''),TYPE construct can be used to concatenate text. The .value('text()[1]', 'varchar(max)') function is then used to safely extract the result from the XML, and finally the STUFF() function is used to strip out the leading separator (comma-space).
;WITH Data AS (
SELECT
Company,
ColumnName,
Value,
ROW_NUMBER() OVER(PARTITION BY Company ORDER BY Value DESC, ColumnName) AS Ord
FROM #b
UNPIVOT (
Value FOR ColumnName IN (A1, A2, A3, A4, B1, G1, G2, G3, HH5, SS6)
) U
)
SELECT B.Company, C.Top5, C.Bottom5
FROM #b B
CROSS APPLY (
SELECT
STUFF((
SELECT ', ' + D.ColumnName
FROM Data D
WHERE D.Company = B.Company
AND D.Ord BETWEEN 1 AND 5
ORDER BY D.ORD
FOR XML PATH(''),TYPE
).value('text()[1]', 'varchar(max)'), 1, 2, '') AS Top5,
STUFF((
SELECT ', ' + D.ColumnName
FROM Data D
WHERE D.Company = B.Company
AND D.Ord BETWEEN 6 AND 10
ORDER BY D.ORD
FOR XML PATH(''),TYPE
).value('text()[1]', 'varchar(max)'), 1, 2, '') AS Bottom5
) C
ORDER BY B.Company
See this db<>fiddle fr a demo.
If you also want lists of the top 5 and bottom 5 values, you can repeat the aggregations above while substituting CONVERT(VARCHAR, D.Value) for D.ColumnName where appropriate.