which produces exactly the same result. Note that after the number of grades
for the first two groups are reported in the first two detail rows a blank is printed
for the empno of the third row; this is the rollup way of indicating that this
row contains the subtotal number of grades for the course cs110. A new detail
row follows for cs210 and, since this course is taught only by the employee 019,
the next row contains a subtotal for this course, etc. Finally, the last row, with
blank for the first two columns is the total number of grades for all courses.