sql - 无效的列名 SQL Server 2008

Question

我不断收到一条错误消息，显示“列名无效”'a'。任何人都可以帮忙吗？

Select 
datename(mm,t.gift_date) as month, 
s.campaign as campaign, 
count(s.Campaign) as a
From usga_stage.facts.transactions t, usga_dw.dbo.DimSourceCode s
Where t.trans_source=s.SourceCode
and t.payment_channel = 'Web'
and t.gift_date like '2013%'
Group by month(t.gift_date),Campaign, a

按月（t.gift_date）、活动、a 排序

Answer 1

您不能按 ALIAS 分组，也不需要按聚合字段分组：

Select 
month(t.gift_date) as month, 
s.campaign as campaign, 
count(s.Campaign) as a
From usga_stage.facts.transactions t, usga_dw.dbo.DimSourceCode s
Where t.trans_source=s.SourceCode
and t.payment_channel = 'Web'
and t.gift_date like '2013%'
Group by month(t.gift_date),Campaign

您可以在该部分中使用别名，但ORDER BY不能GROUP BY

此外，使用显式连接是一种很好的做法，如下所示：

SELECT month(t.gift_date) as month
      ,s.campaign as campaign
      ,count(s.Campaign) as a
FROM usga_stage.facts.transactions t
JOIN usga_dw.dbo.DimSourceCode s
  ON t.trans_source = s.SourceCode
WHERE t.payment_channel = 'Web'
  and t.gift_date like '2013%'
GROUP BY MONTH(t.gift_date)
        ,Campaign