SQLZoo SELECT from Nobel Tutorial #8 solution using single join, no sub-query

gistfile1.sql

SELECT DISTINCT a.yr
  FROM nobel a
  LEFT OUTER JOIN nobel b 
    ON a.yr=b.yr
    AND b.subject NOT IN ('Economics','Literature','Medicine','Peace','Physics')
  WHERE b.subject IS NULL
    AND a.subject = 'Physics'

Your query was really very good. But, how did you know the subjects without any query?
So, I think it would be better to modify your query as follows:

SELECT DISTINCT n1.yr
FROM nobel n1 LEFT OUTER JOIN nobel n2 ON (n1.yr = n2.yr AND n2.subject = 'Chemistry')
WHERE n1.subject = 'Physics' AND n2.subject IS NULL