Which statement is true regarding a noncorrelated subquery?

• A. the subquery is known as a virtual table
• B. the subquery can run as a stand-alone query
• C. the outer query passes a value to the inner query
• D. the subquery must be enclosed in brackets

Answer: (B)

A noncorrelated subquery is indeed a stand-alone query that retrieves data independently of the outer query. This characteristic is what makes the statement that the subquery can run as a stand-alone query correct. In essence, a noncorrelated subquery executes once, and the result is then used by the outer query. This is different from a correlated subquery, where the inner query depends on values from the outer query.

In the context of other options, while a noncorrelated subquery may effectively act like a virtual table in some database environments, it does not universally hold that the subquery is always recognized as such. The outer query typically does not pass a value to the inner query in a noncorrelated subquery, which differentiates it from correlated subqueries. Lastly, while subqueries can be enclosed in brackets for clarity or syntax requirements, it is not a strict requirement for them to be enclosed in brackets for noncorrelated subqueries specifically. Therefore, the assertion that the subquery can run as a stand-alone query is the most accurate statement regarding noncorrelated subqueries.