How to concatenate the values of two fields in Oracle?

In Oracle, you can concatenate two field values using the || operator.

For example, if there is a table named employees with two columns first_name and last_name, and we want to concatenate the values of these two columns into a new column called full_name, we can use the following query statement:

SELECT first_name || ' ' || last_name AS full_name
FROM employees;

The above query will concatenate the values of the first_name and last_name fields with a space separator to create a new field called full_name.