Re: Selecting pairs of numbers

On 10/05/2015 12:00 PM, Raymond O'Donnell wrote:
> On 05/10/2015 19:53, Adrian Klaver wrote:
>> 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(at)test=> create table pr_test(x int, y int);
>>
>> aklaver(at)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
>
> As simple as that? Thank you! I knew there had to be an easy way.

Yea, surprised me to.

>
> Thanks also to the others who replied with a slightly different
> approach, which involved multiplying x by 10.
>
> Ray.
>

--
Adrian Klaver
adrian(dot)klaver(at)aklaver(dot)com