inner-join-lateral

select *
from (
  select distinct student_id
  from class_grade
) as a
inner join lateral (
  select *
  from class_grade as b
  where b.student_id = a.student_id 
  order by score desc
  limit 1
) as tmp on true

白話文 先將class_grade裡面的user_id的唯一一筆取出 然後在將前面的內容的每一筆分別執行inner join lateral的語法(類似for迴圈)