瞭解T-SQL中的PIVOT功能

Question

我對SQL很陌生。

我有這樣的一個表：

ID | TeamID | UserID | ElementID | PhaseID | Effort 
----------------------------------------------------- 
1 | 1 | 1  | 3  | 5  | 6.74 
2 | 1 | 1  | 3  | 6  | 8.25 
3 | 1 | 1  | 4  | 1  | 2.23 
4 | 1 | 1  | 4  | 5  | 6.8 
5 | 1 | 1  | 4  | 6  | 1.5 

，我被告知要得到這樣

ElementID | PhaseID1 | PhaseID5 | PhaseID6 
-------------------------------------------- 
    3  | NULL | 6.74 | 8.25 
    4  | 2.23 | 6.8 | 1.5 

我明白我需要使用旋轉功能的數據。但是不能清楚地理解它。 這將是巨大的幫助，如果有人可以在上述情況下解釋。（或者如果有任何的替代品）

Answer 1

甲PIVOT中找到用過的 將數據從一列轉換爲多列。

對於這裏的例子是一個靜態透視意思是你硬代碼，您要旋轉的列：

create table temp 
(
    id int, 
    teamid int, 
    userid int, 
    elementid int, 
    phaseid int, 
    effort decimal(10, 5) 
) 

insert into temp values (1,1,1,3,5,6.74) 
insert into temp values (2,1,1,3,6,8.25) 
insert into temp values (3,1,1,4,1,2.23) 
insert into temp values (4,1,1,4,5,6.8) 
insert into temp values (5,1,1,4,6,1.5) 

select elementid 
    , [1] as phaseid1 
    , [5] as phaseid5 
    , [6] as phaseid6 
from 
(
    select elementid, phaseid, effort 
    from temp 
) x 
pivot 
(
    max(effort) 
    for phaseid in([1], [5], [6]) 
)p 

這裏是一個SQL Demo一個工作版本。

這也可以通過動態PIVOT完成，您可以動態創建列列表並執行PIVOT。

DECLARE @cols AS NVARCHAR(MAX), 
    @query AS NVARCHAR(MAX); 

select @cols = STUFF((SELECT distinct ',' + QUOTENAME(c.phaseid) 
      FROM temp c 
      FOR XML PATH(''), TYPE 
      ).value('.', 'NVARCHAR(MAX)') 
     ,1,1,'') 

set @query = 'SELECT elementid, ' + @cols + ' from 
      (
       select elementid, phaseid, effort 
       from temp 
      ) x 
      pivot 
      (
       max(effort) 
       for phaseid in (' + @cols + ') 
      ) p ' 


execute(@query) 

兩個結果：

ELEMENTID PHASEID1 PHASEID5 PHASEID6 
3   Null  6.74  8.25 
4   2.23  6.8   1.5 

Answer 2

這些都是非常基本的支點例如好心去通過。從上面的鏈接的產品表

SQL SERVER – PIVOT and UNPIVOT Table Examples

實施例：

SELECT PRODUCT, FRED, KATE 
FROM (
SELECT CUST, PRODUCT, QTY 
FROM Product) up 
PIVOT (SUM(QTY) FOR CUST IN (FRED, KATE)) AS pvt 
ORDER BY PRODUCT 

呈現：

PRODUCT FRED KATE 
-------------------- 
BEER  24 12 
MILK  3  1 
SODA NULL  6 
VEG NULL  5 

類似的例子可以在博客帖子Pivot tables in SQL Server. A simple sample

Answer 3

要設置兼容性錯誤

使用這種使用旋轉功能

ALTER DATABASE [dbname] SET COMPATIBILITY_LEVEL = 100 

Answer 4

SELECT <non-pivoted column>, 
    [first pivoted column] AS <column name>, 
    [second pivoted column] AS <column name>, 
    ... 
    [last pivoted column] AS <column name> 
FROM 
    (<SELECT query that produces the data>) 
    AS <alias for the source query> 
PIVOT 
(
    <aggregation function>(<column being aggregated>) 
FOR 
[<column that contains the values that will become column headers>] 
    IN ([first pivoted column], [second pivoted column], 
    ... [last pivoted column]) 
) AS <alias for the pivot table> 
<optional ORDER BY clause>; 

USE AdventureWorks2008R2 ; 
GO 
SELECT DaysToManufacture, AVG(StandardCost) AS AverageCost 
FROM Production.Product 
GROUP BY DaysToManufacture; 

    DaysToManufacture   AverageCost 
0       5.0885 
1       223.88 
2       359.1082 
4       949.4105 

    -- Pivot table with one row and five columns 
SELECT 'AverageCost' AS Cost_Sorted_By_Production_Days, 
[0], [1], [2], [3], [4] 
FROM 
(SELECT DaysToManufacture, StandardCost 
    FROM Production.Product) AS SourceTable 
PIVOT 
(
AVG(StandardCost) 
FOR DaysToManufacture IN ([0], [1], [2], [3], [4]) 
) AS PivotTable; 




Here is the result set. 
Cost_Sorted_By_Production_Days 0   1   2   3  4  
AverageCost      5.0885 223.88 359.1082 NULL 949.4105 

Answer 5

之前，我是新來這和我創建一個不錯的職位...我的問題米是瞭解如何正確運用聚集，這裏是我的帖子： http://jaider.net/posts/1176-pivot-in-sql-server-correct-aggregated-results/

在@bluefeet的解決方案，它一提的是elementid是你的「隱形」 Group By鍵列是很重要的。 此外，您可以替換elementid或添加更多列，如userid。