How to ensure uniqueness of one column but partition by another key?

[Richard Xiong]

create table tp
(
id varchar(32) not null default '',
platTime datetime not null default '1000-01-01 00:00:00',
primary key (id),
}
type = InnoDB;

there is a primary key id, but I want to use platTime to partition the table, the condition is to ensure the uniqueness by id. How ?