加入在查询中有效，但在视图脚本中无效

Question

我有一个带有连接的查询，可以直接执行它（所以没有“创建视图”部分）。对于某些行，我从子查询 T3 中获得了平均持续时间。但是，当我使用完全相同的查询构建视图并从该视图中选择所有行时，连接不起作用。我在有值的地方得到 NULL 作为 averageDuration，直接执行查询。这怎么可能？

代码使用视图。每个以“V_”开头的表名实际上都是一个视图。 为了让这个脚本作为视图工作，我需要将子查询 T3 中与 V_Operationroom 的连接更改为普通表而不是视图。这个解决方案的奇怪之处在于表或视图 (V_)Operationroom 中使用的字段（Operationroom_Skey 和 IndOperationroom）在表和视图中具有相同的数据类型。视图实际上从表中获取它们 (SELECT Operationroom_Skey, IndOperationroom FROM Operationroom)。

CREATE VIEW [dbo].[V_WaitingList]
AS
    
SELECT  T1.Operationnumber, T3.AverageDuration

FROM V_Operation T1                                                                     
    
    LEFT JOIN V_Operationcode T2    ON  T1.Operationcode_Skey = T2.Operationcode_Skey                                                                       

    LEFT JOIN   (
                    SELECT  
                        S5.Operationcode,
                        AVG(S1.duration) AS AverageDuration
                    FROM V_F_Operatie S1
                        LEFT JOIN V_Operation S2 ON S1.Operation_SKey = S2.Operation_SKey
                        LEFT JOIN V_Operationroom S3 ON S1.Operationroom_Skey = S3.Operationroom_Skey
                        LEFT JOIN V_Operationcode S5 ON S2.Operationcode_Skey = S5.Operationcode_Skey   
                    WHERE   
                        S5.Operationcode IS NOT NULL AND
                        S3.IndOperationroom = '1'
                    GROUP BY    
                        S5.Operatieverrichtingcode

    )   T3  ON  T3.Operationcode = T2.Operationcode

GO

Answer 1

尝试使用 CTE 而不是像下面这样的普通子查询；

CREATE VIEW [dbo].[V_WaitingList] AS
WITH CTEView AS (
     SELECT S5.Operationcode,
            AVG(S1.duration) AS AverageDuration
            FROM V_F_Operatie S1
            LEFT JOIN V_Operation S2 ON S1.Operation_SKey = S2.Operation_SKey
            LEFT JOIN V_Operationroom S3 ON S1.Operationroom_Skey = S3.Operationroom_Skey
            LEFT JOIN V_Operationcode S5 ON S2.Operationcode_Skey = S5.Operationcode_Skey   
            WHERE S5.Operationcode IS NOT NULL AND S3.IndOperationroom = '1'
            GROUP BY S5.Operatieverrichtingcode
)
SELECT  T1.Operationnumber, T3.AverageDuration
FROM V_Operation T1                                                                     
LEFT JOIN V_Operationcode T2 ON T1.Operationcode_Skey = T2.Operationcode_Skey                                                                       
LEFT JOIN CTEView T3 ON T3.Operationcode = T2.Operationcode