-- cte with test data
;with T (ID, Product_Image) as
(
select 300, '/300-01.jpg' union all
select 300, '/300-02.jpg' union all
select 301, '/301.jpg' union all
select 302, '/302.jpg'
)
select
T.ID,
(select T2.Product_Image+'; '
from T as T2
where T.ID = T2.ID
for xml path(''), type).value('.[1]', 'nvarchar(max)') as Product_Images
from T
group by T.ID
Результат:
ID Product_Images
---- -------------------------
300 /300-01.jpg; /300-02.jpg;
301 /301.jpg;
302 /302.jpg;