Does an `ORDER BY` Clause in a Subquery Actually Help?

Is an 'Order By' Clause Beneficial in a Subquery?

Using an 'order by' clause in a subquery raises the question of whether it is a beneficial practice. The answer, however, is a decisive 'no'. Conceptually, it serves no purpose.

The subquery is embedded within an outer query that ultimately determines the order of the results. Therefore, any ordering imposed by the 'order by' clause in the subquery becomes redundant. Furthermore, ordering in SQL does not inherit by default.

The order of results from the outer query remains unaffected regardless of the ordering specified in the subquery. As a result, using 'order by' in a subquery is generally considered pointless.

While specific RDBMS implementations may behave differently due to their individual characteristics, relying on such implementation-specific behaviors is inadvisable.

Exception: If the subquery utilizes 'TOP' or 'LIMIT' clauses, then an 'order by' clause becomes necessary to determine the subset of results to be selected. However, it is important to note that these clauses are not part of standard SQL specifications.

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