Database: dog_kennels
Question: Which professionals have done at least two treatments? List the professional's id, role, and first name.
SQL: select t1.professional_id ,  t1.role_code ,  t1.first_name from professionals as t1 join treatments as t2 on t1.professional_id  =  t2.professional_id group by t1.professional_id having count(*)  >=  2