SELECT DISTINCT T1.first_name ,  T1.last_name FROM Professionals AS T1 JOIN Treatments AS T2 WHERE cost_of_treatment  <  ( SELECT avg(cost_of_treatment) FROM Treatments )
Which professionals have operated a treatment that costs less than the average? Give me theor first names and last names.
SELECT DISTINCT T1.first_name , T1.last_name FROM Professionals AS T1 JOIN Treatments AS T2 WHERE cost_of_treatment < ( SELECT avg ( cost_of_treatment ) FROM Treatments )
select distinct t1 . first_name , t1 . last_name from professionals as t1 join treatments as t2 where cost_of_treatment < ( select avg ( cost_of_treatment ) from treatments )
Which professionals have operated a treatment that costs less than the average ? Give me theor first names and last names .