I have an existing field in a table that its charset is set none. This
field is use for input chinese characters or alphanumeric character.
What will happen if I change this field charset to GB_2312? What will
happen to the chinese characters in it?

Any chinese programmer here? I have a application where in the user
input chinese character, after that the application could export it to
excel. I using NJ Star Communicator to input/view chinese character.
Everthing works fine under english windows enviroment until one day the
excel file produce by the application can not be very correctly under
chinese windows. The chinese characters where like garbage characters
instead. Why? Has the charset has something to do with this?