I'm trying to get a hint as to how i can solve this problem:
i have a table:
n | t
---+--- 1 | 2 1 | 5 2 | 3 2 | 5 3 | 4 3 | 3
(6 rows)
now i want to find the pairs (n1,n2) where no t's collide - eg in this
table it would be (1,3) and (3,1).
Note - this is not homework ;-)
what i'm actually trying to do is to extract n=(countyid,roadid)
t=housenumber - and find out which roads that *cannot* cross county
border because their housenumbers collide (to this i've already narrowed
the n's depending on roadname).