INT データ型に対する ZEROFILL の用途は何ですか?

mysql> Create Table showzerofill(Val1 INT(5) ZEROFILL, Val2 INT(5));
Query OK, 0 rows affected (0.09 sec)

mysql> Insert into showzerofill(Val1, Val2)
values(1,1>,<12,12>,<123,123>,<1234,1234>,<12345,12345>;
Query OK, 5 rows affected (0.03 sec)
Records: 5 Duplicates: 0 Warnings: 0

mysql> Select * from showzerofill;

+-------+-------+
| Val1  | Val2  |
+-------+-------+
| 00001 |     1 |
| 00012 |    12 |
| 00123 |   123 |
| 01234 |  1234 |
| 12345 | 12345 |
+-------+-------+
5 rows in set (0.00 sec)