List the date of each treatment, together with the first name of the professional who operated it.
create table treatments (date_of_treatment varchar, professional_id varchar, PRIMARY KEY (date_of_treatment)); create table professionals (first_name varchar, professional_id varchar, PRIMARY KEY (first_name))
select t1.date_of_treatment, t2.first_name from treatments as t1 join professionals as t2 on t1.professional_id = t2.professional_id