LDD :
DECLARE @temp TABLE
(
Reg_No INT
, Student_Name VARCHAR(20)
, Subject1 INT
, Subject2 INT
, Subject3 INT
, Subject4 INT
, Total INT
)
INSERT INTO @temp (Reg_No, Student_Name, Subject1, Subject2, Subject3, Subject4, Total)
VALUES
(101, 'Kevin', 85, 94, 78, 90, 347),
(102, 'Andy ', 75, 88, 91, 78, 332)
Requête n° 1 - ROW_NUMBER :
SELECT Reg_No = CASE WHEN rn = 1 THEN t.Reg_No END
, Student_Name = CASE WHEN rn = 1 THEN t.Student_Name END
, t.[Subject]
, Total = CASE WHEN rn = 1 THEN t.Total END
FROM (
SELECT
Reg_No
, Student_Name
, [Subject]
, Total
, rn = ROW_NUMBER() OVER (PARTITION BY Reg_No ORDER BY 1/0)
FROM @temp
UNPIVOT
(
[Subject] FOR tt IN (Subject1, Subject2, Subject3, Subject4)
) unpvt
) t
Requête n° 2 – APPLICATION EXTÉRIEURE :
SELECT t.*
FROM @temp
OUTER APPLY
(
VALUES
(Reg_No, Student_Name, Subject1, Total),
(NULL, NULL, Subject2, NULL),
(NULL, NULL, Subject3, NULL),
(NULL, NULL, Subject4, NULL)
) t(Reg_No, Student_Name, [Subject], Total)
Plan de requête :
Coût de la requête :
Sortie :
Reg_No Student_Name Subject Total
----------- -------------------- ----------- -----------
101 Kevin 85 347
NULL NULL 94 NULL
NULL NULL 78 NULL
NULL NULL 90 NULL
102 Andy 75 332
NULL NULL 88 NULL
NULL NULL 91 NULL
NULL NULL 78 NULL
PS : Dans votre requête de cas avec OUTER APPLY est plus rapide que ROW_NUMBER solution.
