UPDATE scores AS sc
SET passed = TRUE
FROM (
 SELECT subject_code ,AVG(score) AS avg
  FROM scores
  GROUP BY subject_code
   )AS sub
   
  WHERE sc.subject_code = sub.subject_code
   AND  sc.score >= sub.avg;
  
 UPDATE scores AS sc
 SET passed=FALSE
 
 WHERE passed is NULL;
 
  SELECT * FROM scores;