Description: A nested query, also known as a subquery, is an SQL query that is embedded within another query. This type of query allows for more complex operations by combining multiple levels of data selection. Nested queries can be used in various parts of an SQL statement, such as the SELECT, WHERE, or FROM clauses. Their main advantage lies in the ability to filter and calculate over data sets that depend on the results of other queries, facilitating the retrieval of more specific and detailed information. Additionally, nested queries can enhance the readability of SQL code by breaking down complex tasks into more manageable parts. However, it is important to note that excessive use of nested queries can impact database performance, especially if not optimized properly. In summary, nested queries are a powerful tool in SQL that allows developers and data analysts to perform more sophisticated queries and obtain accurate results.
