Subqueries in SQL

 Subqueries in SQL

Subqueries are SQL statements that are nested within another SQL statement. Subqueries can be used to perform calculations, filter data, or retrieve data from another table. Here's an example:

sql

SELECT name, age

FROM employees

WHERE department = (

    SELECT name

    FROM departments

    WHERE id = 2

);

In this example, we're using a subquery to retrieve the name of the department with an id of 2 from the "departments" table. We're then using that value in the main query to select all employees who work in that department.