Using Logical OR operator with NULL value : OR « Logic Operator « MySQL Tutorial

1. MySQL Tutorial
2. Logic Operator
3. OR

mysql>
mysql> SELECT 0 || NULL;
+-----------+
| 0 || NULL |
+-----------+
|      NULL |
+-----------+
1 row in set (0.00 sec)

mysql> SELECT 1 || NULL;
+-----------+
| 1 || NULL |
+-----------+
|         1 |
+-----------+
1 row in set (0.02 sec)

mysql> SELECT NULL || NULL;
+--------------+
| NULL || NULL |
+--------------+
|         NULL |
+--------------+
1 row in set (0.00 sec)

mysql>
mysql>