通过join进行过滤的思路很赞。怕有的同学看不清楚sql，我这里根据记忆重写一遍：
select a.user_name, b.skill, c.skill
from user1 as a inner join user_skills as b on a.id = b.user_id and b.skill = '念经'
inner join user_skills as c on b.user_id = c.user_id and c.skill = '变化'
where b.skill_level > 0 and c.skill_level > 0;
