What is the purpose of the NVL function in Oracle?

The NVL function in Oracle is used to handle null values. When the first parameter is null, NVL will return the value of the second parameter; when the first parameter is not null, NVL will return the value of the first parameter. This can be used to replace null values with a specified default value in query results or to handle potential empty fields in calculations. For example:

SELECT NVL(column_name, 'default_value') FROM table_name;

This query will replace any NULL values in the column_name field of the table with ‘default_value’.