sql server implements group_concat in mysql, converts columns to rows, and splices strings with delimiters

----Base

A user corresponds to multiple roles. 
Use convert(VARCHAR,role_id) to escape role_id for int type

 ----sql:

select b.user_id ,
　　roles = stuff((select ',' + convert(VARCHAR, t.ROLE_ID) from base_user_role t where b.USER_ID = t.user_id for xml path('')) , 1 , 1 , '') 
from base_user_role  b
group by b.user_id