Re: lines in ER diagrams

["James K. Lowden" <jklowden schemamania org>]

On 23 Apr 2003 15:01:34 -0700, dialist <pvspam-dialist@hacklab.net> wrote:
> I'm unconvinced 1-1 is necessary since you gain nothing by denormalising
> in this way, except to break up a large table into multiple smaller ones
> that really should remain one large table (otherwise why 1-1?). 

You may exceed your database's maximum number of columns per table.  

You may have senstive data in one of the two tables.  Permissions are
easier to manage per table than per column.  

One of the tables may receive data from an external source; its shape may
be predetermined for organizational or technical reasons.  

You may replicate one of the tables to another server.  

Physical reasons, all, I grant.  But that's where the rows live.  :-)  

Regards, 

--jkl