2개의 결과값이 다른데 왜 차이가 나는지 모르겠습니다

1)

select '2023-08-07', student_id, subject_id, class_id from table group by student_id, subject_id, class_id

2)

select student_id, subject_id, class_id from (

select '2023-08-07', student_id, subject_id, class_id from table group by student_id, subject_id, class_id

) group by student_id, subject_id, class_id