Suppose if we provide an empty string for padding on LPAD() or RPAD() functions then MySQL will return NULL as output. Following example will demonstrate it −
Example
mysql> Select LPAD('ABCD',22,'');
+--------------------+
| LPAD('ABCD',22,'') |
+--------------------+
| NULL |
+--------------------+
1 row in set (0.00 sec)
mysql> Select RPAD('ABCD',22,'');
+--------------------+
| RPAD('ABCD',22,'') |
+--------------------+
| NULL |
+--------------------+
1 row in set (0.00 sec)