newbie question: issue on creating blob field on mysql 5.x for windows

rubyonrails-talk
1

I tried to do a migration task as follows: lass CreateAttachmentBlob < ActiveRecord::Migration   def self.up

add_column :posts, :attachment_thumbnail , :binary, :null=>true, :limit=>0.5.megabyte   end

  def self.down     remove_column :posts, :attachment_thumbnail   end end

when I do rake migrate, the following error occurred: Mysql::Error: #42000You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '52428 8.0)' at line 1: ALTER TABLE posts ADD `attachment_thumbnail` blob(524288.0)

Anyone can tell me what happened? I am using rails 1.2.6 now on ruby 1.8.6 and mysql 5.0.45 GPL.