Re: Hospital ERD

In message <bvqkmu$saq$1_at_sparta.btinternet.com>, Roy Hann <rhann_at_globalnet.co.uk> writes

>"Portroe" <fb_at_oooi.com> wrote in message
>news:bvqi77$sea$05$1_at_news.t-online.com...
>> Charge Nurse, Medical Director, personnel officer, Doctor etc of course
>> all have differing functions, and differing interactions with the other
>> attributes
>>
>> the Charge nurse will have hundreds of connected records over a month,
>> ie. medication ordered, The Medical director significantly less etc
>>
>> is there a source for Sample ERDs where I can see how people typically
>> cope with multiple subclasses 'diagramatically' ?
>
>It ain't rocket science.
>
>You just put all the common attributes in one table (the super table), and
>have 1-to-0-or-1 relationships with one or more subtables that have the
>distinct attributes. If the subtables in turn can have further subtables,
>repeat.
>
>Of course the big problem is that none of the graphical conventions were
>designed by anyone who had much of a clue what they were really doing, so
>they can't represent the very important restriction that a table can't
>simultaneously have two (or more) subtables directly referencing it (if
>that's what is required). i.e. you can't draw a diagram that shows that a
>staff member cannot simultaneously be a phlebotomist and a neurosurgeon, or
>salaried and casual.

IIRC all of this was in the ERD diagrams of SSADM 15 years ago.

-- 
Bernard Peek
London, UK. DBA, Manager, Trainer & Author. Will work for money.