通過在SQL Server中將兩個數相除來排序查詢

Question

我有這樣的Sql Server查詢：

Select       * 
             ,Cast(Column1 as float) as Column1Convert
             ,Cast(Column2 as float) as Column2Convert
             ,Column1Convert/Colun2Convert AS [Result] 
From         MyTable 
Order By     Points DESC, Result ASC

但是我收到錯誤：“無效的列名'Column1Convert'。” 第二個錯誤：“無效的列名'Column2Convert'。”

你能告訴我我做錯了什么嗎？

Answer 1

這是因為您在不允許查詢的同一級別中使用別名。 嘗試：

Select       * 
             ,Cast(Column1 as float) as Column1Convert
             ,Cast(Column2 as float) as Column2Convert
             ,Cast(Column1 as float)/Cast(Column2 as float) AS [Result] 
From         MyTable 
Order By     Points DESC, Result ASC

Answer 2

嘗試這個：

SELECT
    Points, Result, Column1Convert, Column2Convert, 
    Column1Convert/Colun2Convert AS [Result]
FROM
(
    Select       * 
                 ,Cast(Column1 as float) as Column1Convert
                 ,Cast(Column2 as float) as Column2Convert
    From         MyTable 
)
Order By    
    Points DESC, 
    (Column1Convert/Colun2Convert) ASC

Answer 3

在SQL Server中，還有另一種訪問字段別名以進行重用的方法（除了嵌套查詢）

SELECT
      Points
    , ca.Column1Convert
    , ca.Column2Convert
    , ca.Column1Convert / ca.Colun2Convert AS [Result]
FROM MyTable
      CROSS APPLY (
                  SELECT
                        CAST(Column1 AS float) AS Column1Convert
                      , CAST(Column2 AS float) AS Column2Convert
            ) AS ca
ORDER BY
      Points DESC
      , [Result] ASC

如果可用，您可能需要使用TRY_CAST（）而不是CAST（）