如何在选择查询中使用别名并将它们加在一起答案

【问题标题】：How to use alias and sum them together in select query如何在选择查询中使用别名并将它们加在一起
【发布时间】：2012-07-13 08:43:32
【问题描述】：

我有以下问题。我想使用别名并将它们添加在一起，但 SQL 不允许这样做。关于如何在不重复查询的情况下解决此问题的任何建议？使用 Microsoft SQL Server 2008

SELECT    
SUM(CASE WHEN rg.category = 'Space' THEN ((rg.score*20)) END) As space,
SUM(CASE WHEN rg.category = 'QPR' THEN ((rg.score*20)) END) As qpr,

(space + qpr) As result
FROM rg_fin As rg JOIN...../*query goes on*/

【问题讨论】：

标签： sql database select

【解决方案1】：

您可以将查询包装为子查询

SELECT *,
  (space + qpr) As result 
FROM
(
  SELECT     
  SUM(CASE WHEN rg.category = 'Space' THEN ((rg.score*20)) END) As space, 
  SUM(CASE WHEN rg.category = 'QPR' THEN ((rg.score*20)) END) As qpr
  ....
 ) subquery

【讨论】：

【解决方案2】：

您可以使用子查询来做到这一点：

select 
  space, 
  qpr, 
  (space + qpr) As result
from (
  select
  SUM(CASE WHEN rg.category = 'Space' THEN ((rg.score*20)) END) As space,
  SUM(CASE WHEN rg.category = 'QPR' THEN ((rg.score*20)) END) As qpr,
  FROM rg_fin As rg JOIN...../*query goes on*/
) as a

【讨论】：

【解决方案3】：

如果要使用别名，则需要将查询包装在另一个查询中：

SELECT space
    , qpr
    , space + qpr as result
FROM
(
    SELECT    
    SUM(CASE WHEN rg.category = 'Space' THEN ((rg.score*20)) END) As space,
    SUM(CASE WHEN rg.category = 'QPR' THEN ((rg.score*20)) END) As qpr,

    (space + qpr) As result
    FROM rg_fin As rg JOIN...../*query goes on*/
) x

或者如果你不需要使用别名，那么你可以重复这些字段：

SELECT    
    SUM(CASE WHEN rg.category = 'Space' THEN ((rg.score*20)) END) As space,
    SUM(CASE WHEN rg.category = 'QPR' THEN ((rg.score*20)) END) As qpr,

    (SUM(CASE WHEN rg.category = 'Space' THEN ((rg.score*20)) END) 
    + SUM(CASE WHEN rg.category = 'QPR' THEN ((rg.score*20)) END)) As result
FROM rg_fin As rg JOIN...../*query goes on*/

【讨论】：

【解决方案4】：

使用派生表

SELECT 
    space,qpr,(space + qpr) As result 
FROM
(
SELECT     
SUM(CASE WHEN rg.category = 'Space' THEN ((rg.score*20)) END) As space, 
SUM(CASE WHEN rg.category = 'QPR' THEN ((rg.score*20)) END) As qpr, 

(space + qpr) As result 
FROM rg_fin As rg JOIN...../*query goes on*/ 
) as t

【讨论】：