无效的列名称SQL Server 2008

Question

我不断收到错误消息，指出“无效列名”为“ a”。 有人可以帮忙吗？

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

按月份排序（t.gift_date），广告系列，

Answer 1

您不能按ALIAS分组，也不需要按汇总字段分组：

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ORDER BY部分中使用别名，而不是GROUP BY

同样，使用显式联接也是一个好习惯，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