In Oracle, the NVL function allows you to replace NULL with the specified expression: it returns the first operand if it is not NULL, and the second operand otherwise.
In MySQL you can use the IFNULL function.
Oracle:
-- Replace NULL SELECT NVL('John', 'N/A') FROM dual; /* John */ -- Replace NULL SELECT NVL(NULL, 'N/A') FROM dual; /* N/A */
MySQL:
-- Replace NULL SELECT IFNULL('John', 'N/A'); /* John */ -- Replace NULL SELECT IFNULL(NULL, 'N/A'); /* N/A */
For more information, see Oracle to MySQL Migration.