Sure! In SQL, a subquery is a query that is embedded within the parentheses of another query. It allows you to use the result of one query as the input for another query. One common use case is to retrieve data from one table based on a condition in another table. For example, let's say we have two tables: 'Customers' and 'Orders'. We can use a subquery to find all customers who have placed an order. The query would look something like this: SELECT * FROM Customers WHERE CustomerID IN (SELECT CustomerID FROM Orders);

Subqueries are a powerful tool in SQL that help us work with complex data scenarios. They can be used to filter, sort, or perform calculations within the main query. One thing to keep in mind is that subqueries can sometimes impact performance, especially if they are nested multiple levels deep. It's always a good idea to optimize your queries and use joins or other techniques when possible. Overall, subqueries are a great way to add flexibility and depth to your SQL queries.