Question

In an SQL query, which SQL keyword is used to implement a subquery?

a) GROUP BY

b) ORDER BY

c) SELECT

d) HAVING

Answer 1

The SQL keyword used to implement a subquery is 'SELECT', which allows a query to be nested within another SQL query.

Step-by-step explanation:

In SQL queries, a subquery is essentially a query nested inside another query. The correct SQL keyword used to implement a subquery is c) SELECT. A subquery can be used in various parts of the main query, including the WHERE clause, HAVING clause, or in the column list of the SELECT statement.

For instance, we could have a query like this:

SELECT employee_id, name FROM employees WHERE department_id IN (SELECT department_id FROM departments WHERE location = 'New York')

This example demonstrates a subquery being used to retrieve all employees who work in a department located in New York. The subquery is the part within the parentheses, executed first to determine the relevant department IDs.