Select 同一个 select 语句中的别名

Question

    i.Notes, SUM(l.Discount) AS Dcount, i.DiscDate, i.DueDate, i.UIMth, i.UISeq, poj.Job, poj.Description, i.UniqueAttchID, i.ReviewerGroup AS RevGrp, SUM(l.GrossAmt) 
                     AS GrossAmt, v.PayTerms, dbo.HQPT.DiscRate, i.InvTotal, DATEDIFF(day,getdate(),i.DiscDate) AS DiscDays,
--Trying to use the DiscDays and Dcount here    
                    if DiscDays, between '20' and '11' THEN sum(Dcount) as YelDisc

我希望有人能在这里帮助我。我对 T-SQL 很陌生。我相信我在这里需要的是一个子查询，但我不确定如何正确格式化它

谢谢

Answer 1

IF是程序流，不是表达式
您不能在另一列中重复使用别名
比较数值结果时，不要用引号将常量值括起来

尝试

CASE WHEN DATEDIFF(day,getdate(),i.DiscDate) between 20 and 11 
         THEN sum(Dcount) 
     ELSE 0 
END as YelDisc

你可以做一个子查询来重用别名，但是对于这样一个相对简单的表达式和你的结果集中的列数，它可能不值得。

Answer 2

您不能在同一查询中引用别名，但您可以执行以下操作：

      select
      i.Notes, 
      SUM(l.Discount) AS Dcount, 
      i.DiscDate, 
      i.DueDate, 
      i.UIMth, 
      i.UISeq, 
      poj.Job, 
      poj.Description, 
      i.UniqueAttchID, 
      i.ReviewerGroup AS RevGrp, 
      SUM(l.GrossAmt) AS GrossAmt, 
      v.PayTerms, 
      dbo.HQPT.DiscRate, 
      i.InvTotal, 
      DATEDIFF(day,getdate(),i.DiscDate) AS DiscDays,

    --Trying to use the DiscDays and Dcount here    
        case
            when DATEDIFF(day,getdate(),i.DiscDate)  between '11' and '20'                 THEN sum(Dcount) 
            when DATEDIFF(day,getdate(),i.DiscDate)  between '20' and '40'         THEN sum(Dcount)/2 
            else 0 -- this is the default case that doesn't match your cases, it could return NULL 
        end as YelDisc

Select 同一个 select 语句中的别名

Select alias in same select statement

sql

select

alias