with first as (
    select
        first_d,
        t1.member_code,
        t1.WEIGHT
    from health_checkup t1
        join (
            select member_code, max(checkup_date) as first_d
            from health_checkup
            group by member_code
        ) t2
        on t1.member_code = t2.member_code and t1.checkup_date = t2.first_d
),
second as (
    select
        t1.member_code,
        t1.WEIGHT
    from health_checkup t1
        join (
            select member_code, checkup_date,
            ROW_NUMBER() OVER (PARTITION BY member_code ORDER BY checkup_date DESC) AS rank
            from health_checkup
        ) t2
        on t1.member_code = t2.member_code and t1.checkup_date = t2.checkup_date
    where t2.rank = 2
)
select
first_d as CK_DATE,
first.member_code as CODE,
LAST_NAME || FIRST_NAME as NAME,
round(first.weight - second.weight, 1) as CHG_WT
from first
join second using (member_code)
join member_mst using (member_code)
where abs(first.weight * 10 - second.weight * 10) >= 50
order by CHG_WT desc, CODE desc;