Problem with primary key with size>256

[Minh Nguyen]

Hi all,
I have a table in SQL Server with a primary key type varchar(512). When I created that table in MySQL the key is converted to TEXT, but I can't not set it as primary key.

mysql> create table abcd(Pkey varchar(512) not null, primary key(Pkey));
ERROR 1170 (42000): BLOB/TEXT column 'Pkey' used in key specification without a
key length

Please help me how to create a table with primary key has size > 256 ?

Thanks,