UPDATE scores AS main SET passed = TRUE	
    FROM (SELECT subject_code, AVG(score) AS score FROM scores GROUP BY subject_code) AS sub
		WHERE main.score >= sub.score
		AND main.subject_code = sub.subject_code;
	
UPDATE scores AS main SET passed = FALSE	
	FROM (SELECT subject_code, AVG(score) AS score FROM scores GROUP BY subject_code) AS sub
		WHERE main.score < sub.score
		AND main.subject_code = sub.subject_code;