if object_id('[tb]') is not null drop table [tb]
go
create table [tb]([name] varchar(2),[num] int)
insert [tb]
select 'qq',1 union all
select 'qq',2 union all
select 'mm',3 union all
select 'aa',2 union all
select 'qq',1 union all
select 'aa',1 union all
select 'mm',2
go

select name,sum(num) as num from tb group by name
/**
name num
---- -----------
aa   3
mm   5
qq   4

(3 行受影响)
**/