--合格の時
update total_scores 
set
    passed = 'TRUE'
where
    total_score >=
    (
        select
            AVG(total_score) as avg 
        from
            total_scores 
        group by
            student_code
    );

--不合格の時
update total_scores 
set
    passed = 'FALSE'
where
    total_score <
    (
        select
            AVG(total_score) as avg 
        from
            total_scores 
        group by
            student_code
    );