SQL Server的單行多列合併到一列

Question

我有臺這樣的

Reg_No  Student_Name   Subject1 Subject2 Subject3 Subject4 Total 
----------- -------------------- ----------- ----------- ----------- ----------- ----------- 
101   Kevin    85   94   78   90   347 
102   Andy     75   88   91   78   332 

從這個我需要創建一個臨時表或表是這樣的：

Reg_No  Student_Name   Subject  Total 
----------- -------------------- ----------- ----------- 
101   Kevin    85   347 
           94   
           78   
           90   
102   Andy     75   332 
           88   
           91   
           78   

有沒有一種方法，我可以在SQL Server這樣做嗎？

Answer 1

檢查this Fiddle

;WITH MyCTE AS 
(
    SELECT * 
    FROM  (
        SELECT Reg_No, 
          [Subject1], 
          [Subject2], 
          [Subject3], 
          [Subject4] 
        FROM  Table1 
      )p 
    UNPIVOT 
    ( 
     Result FOR SubjectName in ([Subject1], [Subject2], [Subject3], [Subject4]) 
    )unpvt 
) 

SELECT T.Reg_No, 
      T.Student_Name, 
      M.SubjectName, 
      M.Result, 
      T.Total 
FROM  Table1 T 
      JOIN MyCTE M 
       ON T.Reg_No = M.Reg_No 

如果你想在休息NULL值，你可以嘗試以下方法：

This is the new Fiddle

這裏是代碼：

;WITH MyCTE AS 
(
    SELECT * 
    FROM  (
        SELECT Reg_No, 
          [Subject1], 
          [Subject2], 
          [Subject3], 
          [Subject4] 
        FROM  Table1 
      )p 
    UNPIVOT 
    ( 
     Result FOR SubjectName in ([Subject1], [Subject2], [Subject3], [Subject4]) 
    )unpvt 
), 
MyNumberedCTE AS 
(
    SELECT *, 
       ROW_NUMBER() OVER(PARTITION BY Reg_No ORDER BY Reg_No,SubjectName) AS RowNum 
    FROM  MyCTE 
) 
SELECT T.Reg_No, 
      T.Student_Name, 
      M.SubjectName, 
      M.Result, 
      T.Total 
FROM  MyCTE M 
      LEFT JOIN MyNumberedCTE N 
       ON N.Reg_No = M.Reg_No 
       AND N.SubjectName = M.SubjectName 
       AND N.RowNum=1 
      LEFT JOIN Table1 T 
       ON T.Reg_No = N.Reg_No 

Answer 2

最簡單的方法是使用一個UNION條款

select Reg_No, Student_Name, Subject1, Total from YourTable union all 
select Reg_No, Student_Name, Subject2, Total from YourTable union all 
select Reg_No, Student_Name, Subject3, Total from YourTable union all 
select Reg_No, Student_Name, Subject3, Total from YourTable 

UNION

將兩個或多個查詢的結果合併到一個結果集 包括屬於所有行聯盟中的所有查詢。 UNION操作與使用來自兩個表的列 的連接不同。

以下是通過使用UNION結果組的兩個 查詢相結合的基本規則：

•數和列的順序必須在所有 查詢相同。

•數據類型必須兼容。

Answer 3

你應該看看PIVOT運算後：

http://technet.microsoft.com/en-us/library/ms177410(v=sql.100).aspx

Answer 4

DDL：

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) 

查詢＃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 

查詢＃2 - OUTER APPLY：

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) 

查詢計劃：

查詢費用：

輸出：

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：與OUTER APPLY你的情況的查詢比ROW_NUMBER解決方案快。