When I run this code, I do not get error 1055. How come it works with me? select emp_no, salary, max(from_date), to_datefrom salarieswhere to_date >sysdate()group by emp_no;

Same here I think the error only happens if you have not disabled 'only full group by' setting As long as the error does not appear, this setting is disabled and the first query works fine

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