Find the max, average, and minimum gpa of all students in each department.
return departments ;return students of  #1 ;return gpas of  #2 ;return max of  #3 for each  #1 ;return average of  #3 for each  #1 ;return minimum of  #3 for each  #1 ;return #4 ,  #5 ,   #6
['select', 'project', 'project', 'group', 'group', 'group', 'union']