SQL IFNULL Function

The IFNULL( ) function is available in MySQL, and not in SQL Server or Oracle. This function takes two arguments. If the first argument is not NULL, the function returns the first argument. Otherwise, the second argument is returned. This function is commonly used to replace NULL value with another value. It is similar to the NVL function in Oracle and the ISNULL Function in SQL Server.

For example, if we have the following table,

Table Sales_Data

store_name	Sales
Store A	300
Store B	NULL

The following SQL,

SELECT SUM(IFNULL(Sales,100)) FROM Sales_Data;

returns 400. This is because NULL has been replaced by 100 via the ISNULL function.