How to modify ENUM datatypes?

["D. Dante Lorenso" <dante(at)lorenso(dot)com>]

All,

In the past I have used foreign keys to lookup tables for small lists of 
values that I now think ENUM could do the job of.  I was hoping that by 
using ENUM, I would avoid having to do joins in my queries, and that I'd 
be making the data more robust and faster.

I used to have a table for account_status:

  A | Active
  B | Billing Failed
  C | Closed
  D | Deactivated

  account.acct_type CHAR references account_type.acct_type CHAR

But, now I've converted that to an ENUM:

  ACTIVE
  BILLING_FAILED
  CLOSED
  DEACTIVATED

  account.acct_type ENUM account_type

The problem is that once I create a column in my account table that uses 
this 'account_type' datatype, I can't seem to change or add to it any 
more.  I want to add a new value or edit/delete an existing one.

How do you make changes to an ENUM datatype that is already in use?

-- Dante