Re: 3NF question

Elves wrote:
> Hello
>
> I am still not sure about meaning of 3NF
>
> Let's say I've got a table, named USERS:
>
> Id Login Pass Description
>
> Id was selected as a key, but login has to be unique, so it's also a
> key. There are dependencies:
>
> Id -> Pass, Description
> Login -> Pass, Description
> Id -> Login
> Login -> Id
>
> is this 3NF or should it be decomposed to two tables like this:
>
> Id Login
> Login Pass Description
>
> thanks in advance, Elves

In your example ... ID is without purpose which is pretty much the case for any column misnamed ID. Try this instead:

LOGIN_ID
LOGIN_PWD If you want to get a bit more complete add:

EXPIRATION_DATE
STATUS_FLAG

-- 
Daniel A. Morgan
University of Washington
damorgan_at_x.washington.edu
(replace 'x' with 'u' to respond)