Description: The external query in SQL refers to the main query executed within a subquery structure. In this context, a subquery is a nested query within another query, which can be used to filter, calculate, or provide additional data that the main query needs for execution. The outer query can access the results of the subquery and use them to perform more complex operations. This approach allows database developers to perform more efficient and organized queries, facilitating the retrieval of specific information without the need to execute multiple independent queries. Outer queries are particularly useful in situations where data from different tables needs to be compared or calculations based on intermediate results need to be performed. Proper use can significantly improve the readability and performance of SQL queries, allowing users to obtain more accurate and relevant results in their data analysis.
