NVL example
In this example, when the function selects the title and
price for all books, if the price for a title is NULL, the price displays
as 0.00
SELECT title, nvl(price, 0.00) AS price FROM titles;
The nvl function is equivalent to the SQL coalesce function. The result of this expression is type compatible with both expr1 and expr2, as in the coalesce function.