On 10/05/2015 11:39 AM, Raymond O'Donnell wrote:
Hello all,
I have an SQL problem which ought to be simple, but I can't get my head
around it.
I have pairs of integers - let's call them (x, y). In effect, x is a
category, while y is an item within that category. For every x, there is
always the same number of integers y; and both x and y are always
numbered sequentially starting from 1.
My problem is that I need to select a list of these pairs, ordered first
on x and then on y, from a given starting point to a given finishing
point and including all pairs in between.
For example, I might have:
x | y
-----
1 | 1
1 | 2
1 | 3
1 | 4
2 | 1
2 | 2
2 | 3
2 | 4
(etc)
I then might want to extract a list from, say, (1, 3) to (3, 2), giving:
x | y
-----
1 | 3
1 | 4
2 | 1
2 | 2
2 | 3
2 | 4
3 | 1
3 | 2
For the life of me, I can't figure out how to do this. Any help will be
appreciated, or even just a pointer in the right direction. There's
probably something simple that I'm just not seeing....
aklaver@test=> create table pr_test(x int, y int);
aklaver@test=> select * from pr_test where (x, y) between (1, 3) and
(3,2) order by x,y;
x | y
---+---
1 | 3
1 | 4
2 | 1
2 | 2
2 | 3
2 | 4
3 | 1
3 | 2
If anyone's interested, these numbers represent channels and pistons on
the combination system of a largish pipe organ... it's for a hobby project.
Many thanks in advance!
Ray.
--
Adrian Klaver
adrian.klaver@xxxxxxxxxxx
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