create a matrix of subtractions in sql - sql-server

Question

I have a table like this:
id_nbr t1 t2 t3 t4 t5 t6
1111 10 20 30 40 50 40
2222 40 10 50 20 70 90
And I would like to build a function that for each id_nbr will return the max substraction and the time diffrence for that substraction - for example:
for id_nbr 1111 the max is 40 from t1 to t5 so the function will return 40 and 4 (5-1) in diffent cells.
for id_nbr 2222 the max is 60 from t2 to t5 so the function will return 60 and 3 (5-2) in diffrennt cells.
Output:
exec find_max_and_time (1111)
max_diff time
40 4
Any help creating such kind of function?
the function suggested here in a query:

Answer 1

Here one possible solution via unpivot. The idea is to turn your six columns into rows, geth their rowindex which represents the time (according to your example) and then get min and max value of the corresponding columns. However, you should consider handling of duplicates: it might happen, that two columns have the same value and with this you can have multiple matching records for min and max.
DECLARE #t TABLE(
id_nbr INT
,t1 INT
,t2 INT
,t3 INT
,t4 INT
,t5 INT
,t6 INT
);
INSERT INTO #t VALUES (1111,10,20,30,40,50,40), (2222,40,10,50,20,70,90);
DECLARE #SearchID INT = 2222;
DECLARE #TimeIdxFrom INT = 1;
DECLARE #TimeIdxTo INT = 5;
WITH cteBase AS(
SELECT id_nbr, ROW_NUMBER() OVER (PARTITION BY id_nbr ORDER BY (SELECT 1)) rn, times
FROM (
SELECT id_nbr, t1, t2, t3, t4, t5, t6
FROM #t t) t
UNPIVOT(
times FOR cTime IN (t1, t2, t3, t4, t5, t6)
) u
),
cteMinMax AS(
SELECT id_nbr, MIN(times) MinTime, MAX(times) MaxTime
FROM cteBase
WHERE rn >= #TimeIdxFrom
AND rn <= #TimeIdxTo
GROUP BY id_nbr
)
SELECT --*,
cbMax.rn - cbMin.rn AS TimeSpan,
cbMax.times - cbMin.times AS ValDiff
FROM cteMinMax AS cmm
JOIN cteBase AS cbMin ON cmm.id_nbr = cbMin.id_nbr AND cbMin.times = cmm.MinTime
JOIN cteBase AS cbMax ON cmm.id_nbr = cbMax.id_nbr AND cbMax.times = cmm.MaxTime
WHERE cbMax.id_nbr = #SearchID;

Answer 2

NULL return all calculate values
CREATE TABLE dbo.T
(
id_nbr INT,
t1 INT,
t2 INT,
t3 INT,
t4 INT,
t5 INT,
t6 INT
)
GO
INSERT INTO dbo.T (id_nbr, t1, t2, t3, t4, t5, t6)
VALUES
( 1111, 10, 20, 30, 40, 50, 40 ),
(2222, 40, 10, 50, 20, 70, 90 )
GO
CREATE FUNCTION dbo.find_max_and_time(#Id INT)
RETURNS TABLE
AS RETURN
WITH Desce AS
(
SELECT TOP 1 WITH TIES a.id_nbr , b.*
FROM dbo.T a
CROSS APPLY
(
SELECT 1, a.T1 UNION ALL
SELECT 2, a.T2 UNION ALL
SELECT 3, a.T3 UNION ALL
SELECT 4, a.T4 UNION ALL
SELECT 5, a.T5 UNION ALL
SELECT 6, a.T6
) as b(N,Val)
WHERE id_nbr = #Id OR #Id IS NULL
ORDER BY ROW_NUMBER() OVER(PARTITION BY id_nbr ORDER BY Val DESC)
), Asce AS
(
SELECT TOP 1 WITH TIES a.id_nbr,b.*
FROM dbo.T a
CROSS APPLY
(
SELECT 1, a.T1 UNION ALL
SELECT 2, a.T2 UNION ALL
SELECT 3, a.T3 UNION ALL
SELECT 4, a.T4 UNION ALL
SELECT 5, a.T5 UNION ALL
SELECT 6, a.T6
) as b(N,Val)
WHERE id_nbr = #Id OR #Id IS NULL
ORDER BY ROW_NUMBER() OVER(PARTITION BY id_nbr ORDER BY Val ASC)
)
SELECT
a.id_nbr,
a.Val - b.Val as Val,
a.N - b.N as N
FROM
Desce a
INNER JOIN
Asce b
ON a.id_nbr = b.id_nbr
GO
SELECT * FROM dbo.find_max_and_time (1111)
DROP TABLE dbo.T
DROP FUNCTION dbo.find_max_and_time