adding column on particular id

Hi there
Can somebody please help. I'm wanting to add a column to a particular id number something like

alter table name add something varchar(30) where id=?

Firstly is this possible because I can't find any documentation for this and is there a way around it this particular problem I have.

Thanks and regards
Ray

I'm pretty sure you can't do that. Why don't you just add the column to all the rows and leave it NULL for the ones that don't meet your criteria?

Sorry, but you can't add a column to a table and specify a where clause. Quite frankly, that doesn't make any sense.