在SELECT列表中的其他位置引用别名

Question

我有以下查询:

    select FirstName, LastName,
    Case
     When LastName = 'Jones'
     then 'N/A'
    End as Other,
    Case 
      When Other is not null 
      then 1 
    else 0 as Flag

Flag值取决于Other,但由于Other是别名,Flag字段不识别Other.

我想,我可以在选择中使用选择.Flag有更好的方法来识别Other alias列吗？

Answer 1

由于解析查询的方式,您不能引用SELECT和ORDER BY之外的别名.典型的解决方法是将其埋在派生表中:

SELECT 
  FirstName, LastName, Other, 
  Flag = CASE WHEN Other IS NOT NULL THEN 1 ELSE 0 END
FROM 
(
  SELECT FirstName, LastName,
    CASE WHEN LastName = 'Jones'
     THEN 'N/A'
    END AS Other
  FROM dbo.table_name
) AS x;