SQL 动态 ORDER BY 使用别名

Question

使用 SQL Server，我可以使用别名来订购普通的 SELECT 查询:

SELECT   
   u.FirstName + ' ' + u.LastName as PhysicianName, COUNT(r.Id) as ReferralsCount
FROM     
   Referrals r 
INNER JOIN
   Users u ON r.PhysicianId = u.Id
GROUP BY 
   r.PhysicianId, u.FirstName, u.LastName
ORDER BY 
   PhysicianName

但是，尝试使用动态 ORDER BY 做同样的事情:

SELECT   
   u.FirstName + ' ' + u.LastName as PhysicianName, COUNT(r.Id) as ReferralsCount
FROM     
   Referrals r 
INNER JOIN
   Users u ON r.PhysicianId = u.Id
GROUP 
   BY r.PhysicianId, u.FirstName, u.LastName
ORDER BY 
    CASE WHEN @orderby = 'PhysicianName' THEN PhysicianName END,
    CASE WHEN @orderby = 'ReferralsCount' THEN ReferralsCount END

产生以下错误:

Msg 207, Level 16, State 1, Line 10
Invalid column name 'PhysicianName'.
Msg 207, Level 16, State 1, Line 11 Invalid column name 'ReferralsCount'.

Answer 1

SELECT 中定义的列别名只能在ORDER BY 中单独使用。不是在表达。

您可以按如下方式调整您的原始尝试。

;WITH T
     AS (SELECT u.FirstName + ' ' + u.LastName AS PhysicianName,
                COUNT(r.Id)                    AS ReferralsCount
         FROM   Referrals r
                INNER JOIN Users u
                  ON r.PhysicianId = u.Id
         GROUP  BY r.PhysicianId,
                   u.FirstName,
                   u.LastName)
SELECT *
FROM   T
ORDER  BY CASE
            WHEN @orderby = 'PhysicianName' THEN PhysicianName
          END,
          CASE
            WHEN @orderby = 'ReferralsCount' THEN ReferralsCount
          END