Solve this partition puzzle

[santhosh edukulla]

I have a table structure as below:

CREATE TABLE U
(
id bigint(11) unsigned NOT NULL,
creationdate Date NOT NULL,
primary key(id,creationdate)
)ENGINE=InnoDB DEFAULT CHARSET=latin1
PARTITION BY LIST (DAY(creationdate))
(
PARTITION p1 VALUES IN (1) ENGINE = InnoDB,---------------

)
etc

partitioned by date. If we see the table, it has (id,creationdate) as partition.

With this id's entered per date are coming as unique. But, on next day again these id's are appearing again.
But, i want also the id of this table to be unique.

If we keep a unique check on ID, it is crying fould saying that
A UNIQUE KEY must include all columns in the table's partitioning function

How to go about this? Any idea?

Thx,
Santhosh