mysql> INSERT INTO t1 VALUES(2000,1,1),(2000,1,20),(2000,1,30),(2000,2,2)
    -> (2000,2,23),(2000,2,23);
Query OK, 6 rows affected (0.03 sec)
Records: 6 Duplicates: 0 Warnings: 0

mysql> select * from t1;
+------+-------+------+
| year | month | day |
+------+-------+------+
| 2000 | 01 | 01 |
| 2000 | 01 | 20 |
| 2000 | 01 | 30 |
| 2000 | 02 | 02 |
| 2000 | 02 | 23 |
| 2000 | 02 | 23 |
+------+-------+------+
6 rows in set (0.02 sec)

DROP PROCEDURE IF EXISTS `test`.`sp_zerofill`$$

CREATE PROCEDURE `test`.`sp_zerofill`(IN num int)
BEGIN
  declare i int default 1;
  -- initialization value
  set @sqltext = 'insert into lk14 values(0,''char0'')';
  -- begin while
  while i < num do
    set @sqltext = concat(@sqltext,',','(',i,',''char',ceil(num*rand()),''')');
    set i = i + 1;
  end while;
  -- begin dynamic sql
  prepare s1 from @sqltext;
  execute s1;
  deallocate prepare s1;
END$$

DELIMITER ;

select * from lk14 order by id;