If str is longer than len, the return value is shortened to len characters.
mysql>
mysql> SELECT LPAD('ABC',4,'??');
+--------------------+
| LPAD('ABC',4,'??') |
+--------------------+
| ?ABC |
+--------------------+
1 row in set (0.00 sec)
mysql>
mysql> SELECT LPAD('ABC',1,'??');
+--------------------+
| LPAD('ABC',1,'??') |
+--------------------+
| A |
+--------------------+
1 row in set (0.00 sec)
mysql>