GROUP BY is a way to sub-total your results, or perform some
other "aggregate" function on them.
Example:
SELECT department, sum(salary)
FROM tblEmployee
GROUP BY department;
will give you salary totals by department, whereas the sum statement by
itself would just give you the grand total of all salaries in
tblEmployee.
ORDER BY is simply a way to sort your results - it does not affect what
shows up in your resultset, only what order it is displayed.
Example:
SELECT *
FROM tblEmployee
ORDER BY lastname;
will give you all tblEmployee data, in order of last name. If you want
the results in descending (reversed) order, simply add DESC to the end
of the clause:
ORDER BY lastname DESC;
