Re: Selecting pairs of numbers

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.

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

Ray.

--
Raymond O'Donnell :: Galway :: Ireland
rod(at)iol(dot)ie