What is the highest, lowest, and average student GPA for every department?
return departments ;return students of #1 ;return GPA of #2 ;return highest of #3 for each #1 ;return lowest of #3 for each #1 ;return average of #3 for each #1 ;return #4 ,  #5 ,   #6
['select', 'project', 'project', 'group', 'group', 'group', 'union']