sql - 不使用 group by 返回列的总和

Question

以下sql...

declare @parent table (id int, description varchar(50))
declare @child table (parentid int, amount money)

insert into @parent(id, description) values (1, 'test')

insert into @child(parentid, amount) values (1, 3)
insert into @child(parentid, amount) values (1, 3)

select p.*,
       sum(c.amount) as amount
    from @parent p         
        inner join @child c on c.parentid = p.id

生成以下错误...

Msg 8120, Level 16, State 1, Line 10
Column '@parent.id' is invalid in the select list because it is not contained in either an aggregate function or the GROUP BY clause.

这解决了它...

select p.*,
       sum(c.amount) as amount
    from @parent p         
        inner join @child c on c.parentid = p.id
    group by p.id,
             p.description

如何更改它以便查询返回子记录的总和，但不使用 group by 表达式？也许是某种子查询？

Answer 1

您可以使用窗口功能:

select distinct p.*, sum(c.amount) over (partition by p.id) as amount
from @parent p inner join 
     @child c 
     on c.parentid = p.id;

您还可以使用应用:

select distinct p.*, c.amount 
from @parent p cross apply
     (select sum(c.amount) as amount 
      from @child c 
      where c.parentid = p.id
     ) c;