A了两题,还有一个没写 第一题 select count(a.role_id), round(avg(match_cnt), 4), count(case when b.role_id is not null then b.role_id end), round(avg(case when b.role_id is not null then b.battle end), 4) from ( select role_id, count(1) as match_cnt from success group by role_id ...