通过在SQL Server中将两个数相除来排序查询

Question

I've got Sql Server Query like this:

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

But I'am receiving error: "Invalid column name 'Column1Convert'." and second error: "Invalid column name 'Column2Convert'."

Could You tell me what I'am doing wrong ?

Answer 1

This is because you are using aliases in the same level of the query which is not allowed. Try:

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

Try this:

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

In SQL Server there is another way to access field aliases for reuse (aside from nested query)

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

If available to you, you may want to use TRY_CAST() instead of CAST()