通過join進行過濾的思路很贊。怕有的同學看不清楚sql，我這里根據記憶重寫一遍：
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 = '念經'
inner join user_skills as c on b.user_id = c.user_id and c.skill = '變化'
where b.skill_level > 0 and c.skill_level > 0;
select a.user_name,b.timestr,b.kills from user1 a join (select a.user_id,a.timestr,a.kills,(select count(1) from user_kills b where a.user_id = b.user_id and b.kills >= a.kills) as cnt from user_kills a group by user_id,timestr,kills having cnt = 1) b on a.id = b.user_id;
