mysql> create table mysql_microsecond ( log_time_prefix timestamp not null default 0, log_time_suffix mediumint not null default 0) engine innnodb;
Query OK, 0 rows affected, 2 warnings (0.00 sec)

mysql> alter table mysql_microsecond add primary key (log_time_prefix, log_time_suffix);
Query OK, 0 rows affected (0.01 sec)
Records: 0 Duplicates: 0 Warnings: 0

mysql> set @a = convert(concat(now(),'.222009'),datetime);
Query OK, 0 rows affected (0.00 sec)

mysql> insert into mysql_microsecond select date_format(@a,'%Y-%m-%d %H-%i-%s'),date_format(@a,'%f');
Query OK, 1 row affected (0.00 sec)
Records: 1 Duplicates: 0 Warnings: 0

mysql> select * from mysql_microsecond;
+---------------------+-----------------+
| log_time_prefix   | log_time_suffix |
+---------------------+-----------------+
| 2009-08-11 17:47:02 |     222009 |
+---------------------+-----------------+
1 row in set (0.00 sec)