Question

我有一个非常通用的查询，它按ID分组并汇总卷并获取最大地址号。当我运行它时，我得到以下记录计数：

SELECT (case when m.participant_id=0 then 100000000 + m.member_id else m.participant_id      END) as PID, 
    max(m.address_no) as address_no, sum(e.volume) as P3M_Vol into dbo.tmp_MC_P3M_FuelsPromo_3      
  from dbo.MonthlyDataMart e 
  inner join dbo.v_sr_member m on e.member_id = m.member_id
  where e.member_type_cd = 'MC' 
    and e.year = 2014 and e.month between 2 and 4 
    and e.tran_code in ('PTSEARN','PREMIUM')
    and not exists (select 1 from dbo.v_DNC d where e.member_id = d.member_id)         
group by (case when m.participant_id=0 then 100000000 + m.member_id else m.participant_id END)

我收到以下消息：

Warning: Null value is eliminated by an aggregate or other SET operation.

(16828 row(s) affected)

然后我删除了查询中的sum（e.volume）列（以下代码:)

SELECT (case when m.participant_id=0 then 100000000 + m.member_id else m.participant_id END) as PID, 
    max(m.address_no) as address_no into dbo.tmp_MC_P3M_FuelsPromo_2        
  from dbo.MonthlyDataMart e 
  inner join dbo.v_sr_member m on e.member_id = m.member_id
  where e.member_type_cd = 'MC' 
    and e.year = 2014 and e.month between 2 and 4 
    and e.tran_code in ('PTSEARN','PREMIUM')
    and not exists (select 1 from dbo.v_DNC d where e.member_id = d.member_id)         
group by (case when m.participant_id=0 then 100000000 + m.member_id else m.participant_id END)

我获得了不同的行数！

Warning: Null value is eliminated by an aggregate or other SET operation.

(34023 row(s) affected)

知道为什么会这样吗？我只删除了聚合函数，行数不一样。我正在使用MS SQL 2000。

Answer 1

Max（）和sum（）函数正在消除此查询中的空值。错误是针对这些函数中的列。受影响的行是由于aggrigate函数在组内没有sum（）。祝你好运

Answer 2

在您正在聚合的值中使用ISNULL。仔细查看查询中您想要的确切行为！

您的错误行不同的原因是您正在对潜在的NULLS进行分组，聚合和内部联接。根据记录被跳过的位置，您可以得到非常多变的结果。

SQL Server Sum Aggregate函数 - 过滤结果集？

2 个答案: