Ok, i'll put a sample for you.
Imagine this set of records:
ID NAME NUMBER
1 fLIPIS 2
2 gaui 2
3 mYSELF 3
4 yOURSELF 3
5 uNREAL2 4
6 UT 4
Ok, put these records into a table. Then execute these queries:
SELECT FROM TABLE ORDER BY ID ASC;
SELECT FROM TABLE ORDER BY ID DESC;
SELECT FROM TABLE GROUP BY DESC ASC;
SELECT FROM TABLE GROUP BY NUMBER DESC;
SELECT COUNT() FROM TABLE GROUP BY NUMBER ASC;
SELECT COUNT() FROM TABLE GROUP BY NUMBER DESC;
By seeing the results you'll get to know what are these for.
fLIPIS