Re: challenging constraint situation - how do I make it

[Kenneth Downs <ken(at)secdat(dot)com>]

Alban Hertroys wrote:

> When encountering this problem I usually wonder why there isn't a data 
> type that can store a timestamp and can be used to create a UNIQUE 
> INDEX over it's values. That'd be wonderful.
> Well, maybe one day I'll actually have time to create one...
I tried this at trigger level.  The real bear is in the fact that there 
are two columns, not one.  It is trivial to write an exclusion 
constraint that disallows overlapping (including nested) values.  What 
was hard was determining the meta-data structure, how do you have two 
columns that are sometimes treated as one and sometimes as two?

Possible, but devilish in the details.

begin:vcard
fn:Kenneth  Downs
n:Downs;Kenneth 
email;internet:ken(at)secdat(dot)com
tel;work:631-689-7200
tel;fax:631-689-0527
tel;cell:631-379-0010
x-mozilla-html:FALSE
version:2.1
end:vcard