you can apply aggregate property on the column by right click on the column.
after adding aggregation on column you will get a row at bottom that will show aggregate value of that column.
Try to make the last child of the datagrid to be sticky and give the height to the table with respect to the height of screen where you can make the last row of the datagrid as footer row and also you can design the row in the last child class itself.
For that give a class name to the datagrid as example and
//Your code here
Hope this helps.