Re: SQL3 UNDER

On Tue, 23 May 2000, Chris Bitmead wrote:
> If you think the semantics are different provide a specific example
> (including SQL) of how you think their behaviour is different - that is
> how you think UNDER should work differently to current INHERIT.
> 

I'll try to provide examples later.  For now, did you see the gif attachments
on a earlier message of mine?  The UNDER and CLONES/INHERITS gif pictures
provide a graphical view of what I mean.  UNDER creates tree hierarchy down
vertically, while INHERITS supports multiple inheritance in a lateral
direction.  The UNDER trees can be under any table that is part of an INHERITS
relationship.  UNDER and INHERITS work at different levels sorta.  A subtable
in an UNDER hierarchy can't be in an INHERITS clause because it is logically
just part of its maximal supertable.  In other words, INHERITS can provide a
relationship between different whole trees created by UNDER, by way of a
maximal supertable being inherited by another maximal supertable with its own
UNDER tree.  Make any sense? :-)


-- 
Robert B. Easter
reaster@comptechnews.com