A subquery can contain any of the keywords or clauses that an ordinary SELECT query can contain. <br \><br \> Some advantages of the subqueries: <ul> <li \>They allow queries that are structured so that it is possible to isolate each part of a statement. <li \>They provide alternative ways to perform operations that would otherwise require complex joins and unions. <li \>They are, in many people's opinion, readable. Indeed, it was the innovation of subqueries that gave people the original idea of calling the early SQL “Structured Query Language.” </ul>
