select type,SUM(num)num from (
select case TYPE when 2 then '1'+'和2' when 1 then '1'+'和2' else '3' end type,num from tb)a group by type
/*
type    num
1和2    17
3    16
*/

------解决方案--------------------
SQL code

use tempdb 
go
create table tb (type int ,num int)
go
insert tb 
select 1, 2 union all
select 2 ,3 union all
select 3 ,5 union all
select 1 ,4 union all
select 2 ,8 union all
select 3 ,11

select type ,sum(num) as num from (select case when type=1 then '1和2' when type=2 then '1和2' else '3' end type, sum(num) as num  from tb group by type)a group by type

type num
---- -----------
1和2  17
3    16

(2 行受影响)