seyiisq <se************@no-mx.forums.yourdomain.com.au> wrote in
news:se************@no-mx.forums.yourdomain.com.au:
how do i implement a superclass and subclass relatioship of the
type partial disjoint when creating the tables
I'm not sure I understand your terminology.
If you want to have a type/subtype relationship, where there is a
table with all the attributes shared by all the entities, and then
various additional tables with the attributes that apply to only
certain subtypes of those main entities, you implement it with a
main table and the appropriate number of additional tables in a 1:1
relationship. This is done by making the foreign key unique and
required (which is usually the definition of a primary key, but in
this case it's not, as the value is drawn from the main table).
The phrase "partial disjoint" suggests, though, that you may be
talking about JOINs in SQL. In that case, there are 3 types of joins
in Access's Jet SQL, INNER, LEFT and RIGHT. Those can be either
equi- or non-equi-joins (i.e., either using = or > or < or >= or
<=). Equi-joins can be displayed in the Access QBE, while
non-equi-joins (like UNION queries) cannot.
There is another type of join that Jet SQL does not support, the
full outer join, if I'm remembering correctly, but as my SQL
knowledge is almost exclusively derived from working with Jet, I
don't know anything about i.
--
David W. Fenton
http://www.dfenton.com/
usenet at dfenton dot com
http://www.dfenton.com/DFA/ 
