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Posted by strawberry on 03/19/07 14:34
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
;
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