Tôi nghĩ bạn muốn các hàm cửa sổ so sánh giá trị:
select t.*
from (select t.*,
min(t.value) over (partition by t.acct_id) as min_value,
max(t.value) over (partition by t.acct_id) as max_value
from t
) t
where min_value <> max_value;