Question

Regarding the interchangeability of subqueries and joins, which of the following statements is true?

1) a join can always be used as an alternative to a subquery, and a subquery can always be used as an alternative to a join.
2) a join can sometimes be used as an alternative to a subquery, and a subquery can sometimes be used as an alternative to a join.
3) a join can always be used as an alternative to a subquery, and a subquery can sometimes be used as an alternative to a join.
4) a join can sometimes be used as an alternative to a subquery, and a subquery can always be used as an alternative to a join.
5) a join can never be used as an alternative to a subquery, and a subquery can never be used as an alternative to a join.

Answer 1

The statement that is true regarding the interchangeability of subqueries and joins is: (2) a join can sometimes be used as an alternative to a subquery, and a subquery can sometimes be used as an alternative to a join.

Step-by-step explanation:

Subqueries and joins in SQL serve different purposes but can occasionally achieve similar results. Subqueries are useful for returning a single value or a set of values for use in filtering conditions or comparisons. Joins, on the other hand, combine columns from two or more tables based on related columns.

There are scenarios where a subquery can be rewritten using a join, and vice versa, optimizing performance or readability. However, they're not always interchangeable. The choice between them depends on factors like data structure, query complexity, and optimization strategies employed by the database engine.

While a subquery might be easier to understand in some cases, a join can offer better performance. Therefore, it's essential for SQL developers to understand both concepts thoroughly to leverage their strengths effectively for different scenarios.

Correct answer: 2) a join can sometimes be used as an alternative to a subquery, and a subquery can sometimes be used as an alternative to a join.