sql - 左外连接和 PIVOT 之间是否存在一般关系？

Question

我刚开始考虑左外连接，我正在练习 PIVOTS。

我想知道是否可以将此查询转换为数据透视表？

SELECT mydrawercustomer.customerface, 
       mydrawerordertype.ordertypeface, 
       mydrawerorder.LM, 
       Datediff(hour, a1.playdate, a2.playdate) AS [RunningTime1], 
       Datediff(hour, a2.playdate, a3.playdate) AS [RunningTime2], 
       Datediff(hour, a3.playdate, a4.playdate) AS [RunningTime3], 
       Datediff(hour, a1.playdate, a4.playdate) AS [RunningTime4] 
FROM   mydrawerorder 
       LEFT OUTER JOIN mydrawercustomer 
                    ON mydrawerorder.customerKEY = mydrawercustomer.customerKEY 
       LEFT OUTER JOIN mydrawerorderactivity a1 
                    ON mydrawerorder.orderKEY = a1.orderKEY 
                       AND a1.activityKEY = 1 
       LEFT OUTER JOIN mydrawerorderactivity a2 
                    ON mydrawerorder.orderKEY = a2.orderKEY 
                       AND a2.activityKEY = 2 
       LEFT OUTER JOIN mydrawerorderactivity a3 
                    ON mydrawerorder.orderKEY = a3.orderKEY 
                       AND a3.activityKEY = 3 
       LEFT OUTER JOIN mydrawerorderactivity a4 
                    ON mydrawerorder.orderKEY = a4.orderKEY 
                       AND a4.activityKEY = 4 
       INNER JOIN mydrawerordertype 
               ON mydrawerorder.ordertypeKEY = mydrawerordertype.ordertypeKEY 
ORDER  BY mydrawercustomer.customerface, 
          mydrawerordertype.ordertypeface, 
          mydrawerorder.LM, 
          a1.playdate 

我不是要求你为我解决我的挑战，但我只是请求帮助开始将这种类型的左外连接查询转换为 PIVOT。

Answer 1

LEFT JOIN通常和之间的关系PIVOT不是直截了当的，但在您的情况下，可以找到解决方案。

您的查询将如下所示：

select customerface, ordertypeface, LM,
    Datediff(hour, [1], [2]) AS [RunningTime1],
    Datediff(hour, [2], [3]) AS [RunningTime2],
    Datediff(hour, [3], [4]) AS [RunningTime3],
    Datediff(hour, [1], [4]) AS [RunningTime4]
from
(
    SELECT
        c.customerface, 
        ot.ordertypeface, 
        o.LM,
        a.activityKEY,
        a.playdate,
        o.orderKEY
    FROM mydrawerorder o
    INNER JOIN mydrawerordertype ot
        ON o.ordertypeKEY = ot.ordertypeKEY 
    LEFT JOIN mydrawercustomer c
        ON o.customerKEY = c.customerKEY 
    LEFT JOIN mydrawerorderactivity a
        ON o.orderKEY = a.orderKEY 
        and a.activityKEY in (1, 2, 3, 4)
) x
pivot
(
    max(playdate)
    for activityKEY in ([1], [2], [3], [4])
) as pvt
ORDER  BY customerface, ordertypeface, LM, [1]

可以在此处找到根据 PIVOT 使用的其他信息：http ://technet.microsoft.com/en-us/library/ms177410(v=sql.105).aspx