select
    age as AGE,
    case
        when gender_code="20" then "MALE"
        else "FEMALE"
    end as GENDER,
    avg(average_value) as H_AVG
    -- sum(average_value) / count(pf_code) as H_PER
from
    school_health
where
    survey_year between "2019-01-01" and "2019-12-31"
group by
    age,
    gender_code,
    category_code
order by
    AGE desc,
    gender_code desc
;