In this example, we can use GROUP BY not only determined the sort of the rows returned, but also what rows are returned, since we're using TOP to limit the result set.

Let's say we want to return the top 5 highest reputation users from an unnamed popular Q&A site.

Without ORDER BY

This query returns the Top 5 rows ordered by the default, which in this case is "Id", the first column in the table (even though it's not a column shown in the results).

SELECT TOP 5 DisplayName, Reputation
FROM Users

returns...

DisplayName	Reputation
Community	1
Geoff Dalgas	12567
Jarrod Dixon	11739
Jeff Atwood	37628
Joel Spolsky	25784

With ORDER BY

SELECT TOP 5 DisplayName, Reputation
FROM Users
ORDER BY Reputation desc

returns...

DisplayName	Reputation
JonSkeet	865023
Darin Dimitrov	661741
BalusC	650237
Hans Passant	625870
Marc Gravell	601636

Remarks

Some versions of SQL (such as MySQL) use a LIMIT clause at the end of a SELECT, instead of TOP at the beginning, for example:

SELECT DisplayName, Reputation
FROM Users
ORDER BY Reputation DESC
LIMIT 5

SELECT DisplayName, JoinDate, Reputation
FROM Users
ORDER BY JoinDate, Reputation

DisplayName	JoinDate	Reputation
Community	2008-09-15	1
Jeff Atwood	2008-09-16	25784
Joel Spolsky	2008-09-16	37628
Jarrod Dixon	2008-10-03	11739
Geoff Dalgas	2008-10-03	12567

You can use a column's number (where the leftmost column is '1') to indicate which column to base the sort on, instead of describing the column by its name.

Pro: If you think it's likely you might change column names later, doing so won't break this code.

Con: This will generally reduce readability of the query (It's instantly clear what 'ORDER BY Reputation' means, while 'ORDER BY 14' requires some counting, probably with a finger on the screen.)

This query sorts result by the info in relative column position 3 from select statement instead of column name Reputation.

SELECT DisplayName, JoinDate, Reputation
FROM Users
ORDER BY 3

DisplayName	JoinDate	Reputation
Community	2008-09-15	1
Jarrod Dixon	2008-10-03	11739
Geoff Dalgas	2008-10-03	12567
Joel Spolsky	2008-09-16	25784
Jeff Atwood	2008-09-16	37628

Due to logical query processing order, alias can be used in order by.

SELECT DisplayName, JoinDate as jd, Reputation as rep
FROM Users
ORDER BY jd, rep

And can use relative order of the columns in the select statement .Consider the same example as above and instead of using alias use the relative order like for display name it is 1 , for Jd it is 2 and so on

SELECT DisplayName, JoinDate as jd, Reputation as rep
FROM Users
ORDER BY 2, 3

To sort this table Employee by department, you would use ORDER BY Department. However, if you want a different sort order that is not alphabetical, you have to map the Department values into different values that sort correctly; this can be done with a CASE expression:

Name	Department
Hasan	IT
Yusuf	HR
Hillary	HR
Joe	IT
Merry	HR
Ken	Accountant

SELECT *
FROM Employee
ORDER BY CASE Department
         WHEN 'HR'         THEN 1
         WHEN 'Accountant' THEN 2
         ELSE                   3
         END;

Name	Department
Yusuf	HR
Hillary	HR
Merry	HR
Ken	Accountant
Hasan	IT
Joe	IT