|
|
Posted by strawberry on 03/19/07 14:39
On Mar 19, 2:34 pm, "strawberry" <zac.ca...@gmail.com> wrote:
> On Mar 19, 1:41 pm, "Dr. Wolfgang Hintze" <w...@snafu.de> wrote:
>
>
>
> > Suppose we have a table tab ín which there are fields X, Y, ...
> > which designate the coordinates of n-dimensional vectors.
>
> > We would like to select all records which contain the same vectors
>
> > Exapmple n=2
>
> > ID X Y
> > 01 1 2
> > 02 1 3
> > 03 1 2
> > 04 2 3
>
> > The select statement should yield the records with ID 01 and 03
> > (vectors (1,2))
>
> > There might of course be several sets of equal vector records.
>
> > In the end we would like to have a list of all those equal vector
> > records.
>
> > In my practical case n=2 is sufficient but a general formulation would
> > be interesting as well.
>
> > Any help and suggestions would be greatly appreciated.
>
> > Wolfgang
>
> Sorry, I don't understand the implications of n in this problem...
>
> SELECT DISTINCT (v1.id), v2.x, v2.y
> FROM vectors v1
> LEFT JOIN vectors v2 ON v1.id <> v2.id
> WHERE v1.x = v2.x
> AND v1.y = v2.y
> ORDER BY v1.x, v1.y, v1.id
> ;
Oh I see - yes just add an AND for each dimension:
WHERE v1.x = v2.x
AND v1.y = v2.y
AND v1.z = v2.z
AND v1.m = v2.m
AND v1.n = v2.n
AND v1.h = v2.h
AND v1.w = v2.w
AND v1.d = v2.d
Navigation:
[Reply to this message]
|