SQL 内部 select 参考计算值

Question

这几乎可以工作了……

SELECT 
    dbo.ObjectThumb.dotID, dbo.ObjectThumb.doID, 
    dbo.ObjectThumb.dotWidth, dbo.ObjectThumb.dotHeight, 
    dbo.Object.doWidth, dbo.Object.doHeight, 
    (CAST(dotWidth AS FLOAT) / CAST(doWidth AS FLOAT)) AS 'widthRatio', 
    (CAST(dotHeight AS FLOAT) / CAST(doHeight AS FLOAT)) AS 'heightRatio', 
    (SELECT Max(v) FROM (VALUES (widthRatio), (heightRatio)) AS value(v)) AS MaxRatio 
FROM 
   dbo.ObjectThumb 
INNER JOIN 
   dbo.Object ON Object.doID = ObjectThumb.doID

服务器returns一个错误：

Invalid column name widthRatio
Invalid column name heightRatio

这些列是在外部 select 中计算的。如果我引用两个非计算列（例如 doID 和 dotID），我的查询运行s。

我想我搞砸了内部 select 的语法。这将是运行在 SQL Server 2008 R2 (v10.50.2550) 上。

我离那个内栏的正确语法不远了。例如，如果我运行

SELECT * 
FROM (VALUES (1,2), (5,3), (1,4)) AS tableOfValues (columnName1, ColumnName2)

我明白了

1 2
5 3
1 4

我将不胜感激在引用外部 select 中的计算列的语法方面的帮助。如果你能告诉我正确的英语来指示 inner-select、outer-select 和计算列，那将是一个奖励！

Answer 1

这里要理解的重要一点是你的逻辑是行不通的。您不能 select 主查询中的值，在这种情况下，widthRatio 和 heightRatio 来自子 select 或内联查询，因为它超出了该查询的范围.知道您想要做的是创建一个您将加入主查询的内联查询。

您的内联查询应如下所示

Select ObjectThumb.doID As 'LinkID',
    (CAST(dotWidth AS FLOAT) / CAST(doWidth AS FLOAT)) AS 'Ratio'
From ObjectThumb 
    INNER JOIN Object ON Object.doID = ObjectThumb.doID

Union

Select ObjectThumb.doID,
    (CAST(dotHeight AS FLOAT) / CAST(doHeight AS FLOAT))
From ObjectThumb 
    INNER JOIN Object ON Object.doID = ObjectThumb.doID

然后您可以像这样加入您的内联查询

SELECT ObjectThumb.dotID, 
       ObjectThumb.doID, 
       ObjectThumb.dotWidth, 
       ObjectThumb.dotHeight, 
       Object.doWidth, 
       Object.doHeight, 
       (CAST(dotWidth AS FLOAT) / CAST(doWidth AS FLOAT)) AS 'widthRatio', 
       (CAST(dotHeight AS FLOAT) / CAST(doHeight AS FLOAT)) AS 'heightRatio',
       Max(AllRatioTable.Ratio) As MaxRatio
From ObjectThumb 
    INNER JOIN Object ON Object.doID = ObjectThumb.doID
    Inner Join (Select ObjectThumb.doID As 'LinkID',
                    (CAST(dotWidth AS FLOAT) / CAST(doWidth AS FLOAT)) AS 'Ratio'
                From ObjectThumb 
                    INNER JOIN Object ON Object.doID = ObjectThumb.doID

                Union

                Select ObjectThumb.doID,
                    (CAST(dotHeight AS FLOAT) / CAST(doHeight AS FLOAT))
                From ObjectThumb 
                    INNER JOIN Object ON Object.doID = ObjectThumb.doID
                ) As AllRatioTable
        On ObjectThumb.doID = AllRatioTable.LinkID
Group by ObjectThumb.dotID, 
         ObjectThumb.doID, 
         ObjectThumb.dotWidth, 
         ObjectThumb.dotHeight, 
         Object.doWidth, 
         Object.doHeight

还有关于如何称呼您的子select的话题，请看这里：

http://www.allinterview.com/showanswers/81062/what-is-different-between-inline-query-subquery-corelated-query.html

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