The values TRUE and FALSE are merely aliases for 1 and 0, respectively, as shown here: : Boolean « Data Types « MySQL Tutorial

1. MySQL Tutorial
2. Data Types
3. Boolean

mysql>
mysql> SELECT IF(0 = FALSE, 'true', 'false');
+--------------------------------+
| IF(0 = FALSE, 'true', 'false') |
+--------------------------------+
| true                           |
+--------------------------------+
1 row in set (0.00 sec)

mysql> SELECT IF(1 = TRUE, 'true', 'false');
+-------------------------------+
| IF(1 = TRUE, 'true', 'false') |
+-------------------------------+
| true                          |
+-------------------------------+
1 row in set (0.00 sec)

mysql> SELECT IF(2 = TRUE, 'true', 'false');
+-------------------------------+
| IF(2 = TRUE, 'true', 'false') |
+-------------------------------+
| false                         |
+-------------------------------+
1 row in set (0.00 sec)

mysql> SELECT IF(2 = FALSE, 'true', 'false');
+--------------------------------+
| IF(2 = FALSE, 'true', 'false') |
+--------------------------------+
| false                          |
+--------------------------------+
1 row in set (0.00 sec)

mysql>