Description: Nested selection is a technique in SQL that allows for complex queries by embedding a SELECT statement within another SELECT statement. This hierarchical structure enables database developers to efficiently and organizedly extract information from multiple tables. The outer or main query is executed first, and its result is used as input for the inner or nested query. This is particularly useful when filtering data based on results from other queries, facilitating the retrieval of more specific and relevant information. Nested selection can enhance the readability of SQL code, as it allows for breaking down complex queries into more manageable parts. However, it is important to note that excessive use of nested selections can impact database performance, especially with large datasets, due to the additional load of executing multiple queries. In summary, nested selection is a powerful tool in a database developer’s arsenal, enabling the creation of sophisticated queries that can address a variety of analytical and operational needs.
