what are the names of all candidates?
select t1.name from people as t1 join candidate as t2 on t1.people_id = t2.people_id
among them, whose oppose percentage is the lowest?
select t1.name from people as t1 join candidate as t2 on t1.people_id = t2.people_id order by oppose_rate limit 1
for each gender?
select t1.name, t1.sex, min(oppose_rate) from people as t1 join candidate as t2 on t1.people_id = t2.people_id group by t1.sex