sql server - How to do it without the while loop in sql -

i have table this,

a         |        b ---------------------- 1         |       10 1         |       20 2         |       30 2         |       40 

i need output as,

a         |         b ------------------------ 1         |        10,20 2         |        30,40 

thank in advance

try this.

create table #table2(     col1 int,     col2 varchar(10), )  insert #table2 select 1, '10' union select 1, '20' union select 1, '30' union select 2, '40' union select 2, '50' union select 2, '60'   select     col1,     col2 =          stuff((             select                 ', ' + t2.col2             #table2 t2                             t2.col1 = t1.col1             xml path(''), type).value('.', 'varchar(max)'         ), 1, 2, '') #table2 t1 group t1.col1