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    Question

    In SQL, which of the following best describes the role

    of a subquery within a SELECT statement?
    A A subquery is used to update data in a table based on conditions in another table. Correct Answer Incorrect Answer
    B A subquery acts as a standalone query that doesn’t interact with the main query. Correct Answer Incorrect Answer
    C A subquery is used to filter or aggregate data within the main query. Correct Answer Incorrect Answer
    D A subquery can only be used to retrieve a single value. Correct Answer Incorrect Answer
    E A subquery is not supported in SQL queries. Correct Answer Incorrect Answer

    Solution

    Subqueries are embedded SELECT queries within another SELECT, INSERT, UPDATE, or DELETE statement. They are particularly useful for filtering or aggregating data dynamically based on specific criteria from another table or set of data. For instance, a subquery can be used to calculate an average salary for employees within a particular department and then use this value to filter or modify records within the main query. This is essential for complex reporting scenarios where nested logic is required, such as calculating sums, averages, or applying complex conditions across related data sets. Why Other Options Are Incorrect: • A) Update Data: While subqueries can influence the data manipulation in the main query, updating data within a subquery typically involves more complex statements and is not the primary use of subqueries. • B) Standalone Query: Subqueries do interact with the main query and are not completely independent in terms of execution context. • D) Single Value: Subqueries can return multiple values, depending on their structure and what they are designed to query. • E) Unsupported: Subqueries are indeed supported in SQL and are a fundamental part of SQL querying.

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