如何将两个MySQL行合并为一个并使用PHP在表中显示它们？

I have a table "exercise_results". People put in their results at the beginning and then two months later put in their results to see how much they improved. Their beginning set has the exercise_type_id of "1" and the end set has the exercise_type_id of "2".I have a table "exercise_results". People put i