SQL 상위 n % 열 선택

Question

다소 어려운 쿼리가 있습니다. 'key_phrases'라는 테이블 ('user', 'phrase', 'tfw')에 쿼리를 작성해야합니다. 'tfw'열의 값이 가장 높은 각 사용자의 상위 10 % . 쿼리는 모든 열을 반환해야합니다. 사전에 감사, 무기 호

Answer 1

select user, phrase, tfw 
from key_phrases t1 
join (
    select count(*) total_rows_per_user, user 
    from key_phrases 
    group by user 
) t2 on t1.user = t2.user 
where (
    select count(*) from key_phrases t3 
    where t3.user = t1.user 
    and t3.tfw >= t1.tfw 
)/total_rows_per_user <= .1 

select user, phrase, tfw, 
if(@prev_user = user, @user_count := @user_count + 1, @user_count := 1), 
@prev_user := user 
from key_phrases t1 
join (
    select count(*) total_rows_per_user, user 
    from key_phrases 
    group by user 
) t2 on t1.user = t2.user 
cross join (select @user_count := 1, @prev_user := null) t3 
where @user_count/total_rows_per_user >= .9 
order by user, tfw