Difference between "HAVING ... GROUP BY" and "GROUP BY ... HAVING"

I have got the table MYTABLE with 2 columns: A and B

I have got the following pieces of the code:

SELECT MYTABLE.A FROM MYTABLE 
    HAVING SUM(MYTABLE.B) > 100
    GROUP BY MYTABLE.A

and

SELECT MYTABLE.A FROM MYTABLE 
    GROUP BY MYTABLE.A
    HAVING SUM(MYTABLE.B) > 100

Is it the same? Is it possible that these 2 codes will return diffrent sets of results?

Thank you in advance