Which skill is used in fixing the most number of faults? List the skill id and description.
create table skills (skill_id varchar, skill_description varchar, PRIMARY KEY (skill_id)); create table skills_required_to_fix (skill_id varchar, PRIMARY KEY (skill_id))
select t1.skill_id, t1.skill_description from skills as t1 join skills_required_to_fix as t2 on t1.skill_id = t2.skill_id group by t1.skill_id order by count(*) desc limit 1