sql - 使用别名的 SQL 动态 ORDER BY

Question

SELECT使用 SQL Server，我可以使用别名订购普通查询：

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，尝试用动态做同样的事情ORDER BY：

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：

消息 207，级别 16，状态 1，第 10 行
无效的列名称“医师姓名”。
消息 207，级别 16，状态 1，第 11 行无效的列名称“ReferralsCount”。

Answer 1

中定义的列别名SELECT只能ORDER BY在它们自己的中使用。不在一个表达式中。

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