Is order by clause allowed in a subquery

Question

Is there any reason why or why not you should do an \'order by\' in a subquery?

Answer 1

No ORDER BY is valid in a subquery when you are interested in a subset of the overall data, hence you always need a TOP (SQL Server). There's no point having an ORDER BY without TOP in a subquery because the overall ordering of the results is handled by the outer query.