列別名錯誤與SQL Server UDF

Question

我試圖做一個存儲在SQL服務器功能，它將返回我可以加入回到另一個表中值的表，正是如此：

CREATE FUNCTION [dbo].getmedian (@varPartionBy1 int,@varPartionBy2 int, @varForTieBreak int, @varForMeasure int) 
    RETURNS TABLE 
    AS 
    RETURN 
    (
     SELECT 
      @varPartionBy1, 
      @varPartionBy2, 
      AVG(@varForMeasure) 
     FROM 
     (
      SELECT 
       @varPartionBy1, 
       @varPartionBy2, 
       ROW_NUMBER() OVER (
       PARTITION BY @varPartionBy1, @varPartionBy2 
       ORDER BY @varForMeasure ASC, @varForTieBreak ASC) AS RowAsc, 
       ROW_NUMBER() OVER (
       PARTITION BY @varPartionBy1, @varPartionBy2 
       ORDER BY @varForMeasure ASC, @varForTieBreak DESC) AS RowDesc 
      from 
      [fakename].[dbo].[temptable] bp 

     ) bp 
     WHERE 
      RowAsc IN (RowDesc, RowDesc - 1, RowDesc + 1) 
     GROUP BY @varPartionBy1, @varPartionBy2 

    ) 

GO

這是返回錯誤：「消息8155，級別16，狀態2，過程getmedian，第25行 沒有列名的‘BP’第1欄指明。」 - 我想，我不明白如何在UDF上下文中爲列設置表別名。

我應該怎麼做來解決這個錯誤嗎？

這是我的第一個USF所以我很感謝你，而解決這些問題的主要問題的任何其他有用的設計見解。謝謝你的幫助！

Answer 1

如果你有SELECT @varPartionBy1, @varPartionBy2那些需要有分配給他們的列名。您可以將它們分配直接如SELECT @varPartionBy1 AS varPartionBy1或SELECT varPartionBy1 = @varPartionBy1也可以在表的別名) bp(varPartionBy1, varPartionBy2,...

指定了正確的功能很可能是

CREATE FUNCTION [dbo].getmedian (@varPartionBy1 int,@varPartionBy2 int, @varForTieBreak int, @varForMeasure int) 
RETURNS TABLE 
AS 
RETURN 
(
    SELECT 
     varPartionBy1, 
     varPartionBy2, 
     AVG(@varForMeasure) AS AvgVarForMeasure 
    FROM 
    (
     SELECT 
      @varPartionBy1 AS varPartionBy1, 
      @varPartionBy2 As varPartionBy1, 
      ROW_NUMBER() OVER (
      PARTITION BY @varPartionBy1, @varPartionBy2 
      ORDER BY @varForMeasure ASC, @varForTieBreak ASC) AS RowAsc, 
      ROW_NUMBER() OVER (
      PARTITION BY @varPartionBy1, @varPartionBy2 
      ORDER BY @varForMeasure ASC, @varForTieBreak DESC) AS RowDesc 
     from 
     [fakename].[dbo].[temptable] bp 

    ) bp 
    WHERE 
     RowAsc IN (RowDesc, RowDesc - 1, RowDesc + 1) 
    GROUP BY varPartionBy1, varPartionBy2 

) 

Answer 2

好了，一旦你的語法問題的出路，你的問題不會結束。首先，你不能真正做你想要做什麼（傳遞變量的PARTITION BY和ORDER BY條款）。那些只是被視爲常量，所以ROW_NUMBER()將被任意使用。

觀察這裏發生了什麼：

DECLARE @foo SYSNAME = N'name'; 

SELECT name, foo = @foo, -- this is just a constant value, not a column 
    varASC = ROW_NUMBER() OVER (ORDER BY @foo ASC), 
    varDESC = ROW_NUMBER() OVER (ORDER BY @foo DESC), 
    colASC = ROW_NUMBER() OVER (ORDER BY name ASC), 
    colDESC = ROW_NUMBER() OVER (ORDER BY name DESC) 
FROM sys.objects --WHERE is_ms_shipped = 0 
ORDER BY varASC; 

部分結果：

name foo varASC varDESC colASC colDESC 
---- ---- ------ ------- ------ ------- 
t1 name  1  1  1  100 
t2 name  2  2  2  99 
t3 name  3  3  3  98 
t4 name  4  4  4  97 
t5 name  5  5  5  96 
------ only column that deviates ----^^^^^^^ 

爲@foo變量值是每一行相同，因此，劃分和排序由完全無意義的。