Re: Difference in columns

On Sun, May 11, 2008 at 11:07 PM, Mag Gam <magawake(at)gmail(dot)com> wrote:

> Hi All,
>
> I have a view that generates output similar to this.
>
> select * from foo.view;
>
> ts | size
> -------------------+-----
> 2002-03-16 | 11
> 2002-03-17 | 16
>
> 2002-03-18 | 18
> 2002-03-19 | 12
>
> I am trying to find the difference between the size column. So the desired
> output would be
>
> ts | size| Diff
> -------------------+-----+------
> 2002-03-16 | 11 | 0
>
> 2002-03-17 | 15 | 4
> 2002-03-18 | 18 | 3
> 2002-03-19 | 12 | -6
>
>
> I need the first column to be 0, since it will be 11-11. The second colum
> is 15-11. The third column is 18-15. The fourth column is 12-18.
>
> Any thoughts about this?

Try this:

select ts,
size,
t1.size - (select t2.size
from foo.view as t2
where t2.ts < t1.ts
order by ts desc
limit 1) as diff
from foo.view as t1
order by ts asc;

HTH,

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