如何做到這一點沒有while循環SQL

Question

我有這樣一個表，

A   |  B 
---------------------- 
1   |  10 
1   |  20 
2   |  30 
2   |  40 

我需要的輸出，

A   |   B 
------------------------ 
1   |  10,20 
2   |  30,40 

預先感謝您

Answer 1

試試這個。

create table #table2(
    col1 int, 
    col2 varchar(10), 
) 

insert into #table2 
select 1, '10' union all 
select 1, '20' union all 
select 1, '30' union all 
select 2, '40' union all 
select 2, '50' union all 
select 2, '60' 


select 
    col1, 
    col2 = 
     stuff((
      select 
       ', ' + t2.col2 
      from #table2 t2 
      where 
       t2.col1 = t1.col1 
      for xml path(''), type).value('.', 'varchar(max)' 
     ), 1, 2, '') 
from #table2 t1 
GROUP BY t1.col1