mysql>
mysql> SELECT 'A\nB' REGEXP '^A\nB$';
+------------------------+
| 'A\nB' REGEXP '^A\nB$' |
+------------------------+
| 1 |
+------------------------+
1 row in set (0.00 sec)
mysql>
mysql> SELECT 'AB' REGEXP '^A$';
+-------------------+
| 'AB' REGEXP '^A$' |
+-------------------+
| 0 |
+-------------------+
1 row in set (0.01 sec)
mysql>