ifnull
Description
Syntax:
ifnull(expr1, expr2)
If the value of expr1 is not null, this function will return expr1; otherwise, it will return expr2.
Example
mysql> select ifnull(1,0);
+--------------+
| ifnull(1, 0) |
+--------------+
| 1 |
+--------------+
mysql> select ifnull(null,10);
+------------------+
| ifnull(NULL, 10) |
+------------------+
| 10 |
+------------------+Keywords
IFNULL