如何在sql server中对每个id的列中的单元格求和

我是Sql server新手。sumdatediffx，y，z给出了a1和a2的和，而我希望a1和a2的和是分开的。我不知道如何按id分组。我知道sum将返回两者的总和，但我想知道如何将它们分开

select email,
    sum(datediff(day, x, y))
from abc
where users.id ='a1'
    or users.id='a2'
group by email, users.id

email|datex|datey|
a1   |1    |2
a1   |1    |3
a1   |2    |5
a2   |2    |7
a2   |3    |7
a2   |1    |8

那我需要什么

email|diff
a1   |4
a2   |6

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我将输出存储为不带sum的视图，然后按id选择sum组

Create view vwTesting
AS    
select email,
    datediff(day, x, y) as diff
    from abc
    where users.id ='a1'
    or users.id='a2'
    group by email, users.id

第二部分

Select email, sum(diff) from vwTesting group by email

这是对输出的查询

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不，它应该给出每组的总数。您发布的查询将不会编译，因为您不是通过电子邮件分组，而是将其包含在选择列表中。我建议你发布你的实际问题，而不是模型。对不起，这将违反道德规范，但我在组中添加了电子邮件。你对上述问题的回答不正确。如果我没有错，答案应该是a1=6和a2=16。这里的问题是什么？您的查询会给出预期的结果，尽管@ArunGairola所说的结果是6和16，而不是4和6。看见

select  email, sum(datediff(day,datex,datey)) as dd  from (
select 'a1' as email, 1 as datex ,2 as datey
union all 
select 'a1' as email, 1 as datex ,3 as datey
union all 
select 'a1' as email, 2 as datex ,5 as datey
union all 
select 'a2' as email, 2 as datex ,7 as datey
union all 
select 'a2' as email, 3 as datex ,7 as datey
union all 
select 'a2' as email, 1 as datex ,8 as datey
) X 
GRoup BY email