A subquery in an SQL SELECT statement:

Solution (By Examveda Team)

Option A: can only be used with two tables. - This option is incorrect. A subquery in SQL can be used with any number of tables, depending on the complexity of the query.
Option B: can always be duplicated by a join. - This option is incorrect. While some subqueries can be rewritten as joins, not all subqueries can be directly duplicated using joins. It depends on the specific query and its logic.
Option C: has a distinct form that cannot be duplicated by a join. - This is the correct answer. Some subqueries have a unique form or logic that cannot be replicated using a join. Subqueries can often provide more flexible and specific results compared to joins.
Option D: cannot have its results sorted using ORDER BY. - This option is incorrect. Subqueries can have their results sorted using the "ORDER BY" clause, just like regular queries.
Conclusion:
A subquery in an SQL SELECT statement Option C: has a distinct form that cannot be duplicated by a join. This means that some subqueries provide unique functionality or logic that cannot be directly replaced by a join operation. Therefore, the correct answer is has a distinct form that cannot be duplicated by a join.