sqlserver 行列轉換(行傳換為列)

1.原始查詢

SELECT s.Name AS ShiftName,
        h.BusinessEntityID,
        d.Name AS DepartmentName
FROM HumanResources.EmployeeDepartmentHistory h
INNER JOIN HumanResources.Department d
ON h.DepartmentID = d.DepartmentID
INNER JOIN HumanResources.Shift s
ON h.ShiftID = s.ShiftID
WHERE EndDate IS NULL
AND d.Name IN ('Production', 'Engineering', 'Marketing')
ORDER BY ShiftName;

 

結果如下

 

在這個結果集中，我們可以看到所有的部門都列在一個列中。下一步是將此查詢返回的部門值轉換為列，以及按班次計算的員工數。

想要實現的效果

 

 

2.用PIVOT關鍵字進行行列轉換

SELECT  ShiftName,        
                Production,        
                Engineering,        
                Marketing
FROM    (SELECT s.Name AS ShiftName,       
                            h.BusinessEntityID,      
                            d.Name AS DepartmentName         
                FROM   HumanResources.EmployeeDepartmentHistory h                
                INNER JOIN HumanResources.Department d                    
                ON h.DepartmentID = d.DepartmentID                
                INNER JOIN HumanResources.Shift s                    
                ON h.ShiftID = s.ShiftID         
                WHERE  EndDate IS NULL                
                AND d.Name IN ('Production', 'Engineering', 'Marketing')        
                ) AS a
PIVOT
    ( 
    COUNT(BusinessEntityID)
    FOR DepartmentName IN ([Production], [Engineering], [Marketing])
    )  AS b
ORDER BY ShiftName;

結果如下:

 

 

3.轉換的語法如下:

 

 4.參數的定義如下:

 

官網示義

 

 

 

 

 

 

 

 

 

5.在引入PIVOT操作符之前,我們是通過以下語句進行轉換的

SELECT  s.Name AS ShiftName,      
                SUM(CASE WHEN d.Name = 'Production' THEN 1 ELSE 0 END) AS Production,        
                SUM(CASE WHEN d.Name = 'Engineering' THEN 1 ELSE 0 END) AS Engineering,       
                SUM(CASE WHEN d.Name = 'Marketing' THEN 1 ELSE 0 END) AS Marketing
FROM    HumanResources.EmployeeDepartmentHistory h       
INNER JOIN HumanResources.Department d            
ON h.DepartmentID = d.DepartmentID       
INNER JOIN HumanResources.Shift s         
ON h.ShiftID = s.ShiftID
WHERE   h.EndDate IS NULL       
AND d.Name IN ('Production', 'Engineering', 'Marketing')
GROUP BY s.Name;

也是同樣結果

 

 

6.這兩種方法無論是用PIVOT關鍵字還是直接聚合運算都需要事先知道部門的名稱,因為必須要有列名,

這種情況可以先查詢一下部門,然后動態拼接進column_list ,但是這種動態拼接似乎用第二種方式無法實現