Re: nth_value and row_number in a partition

Hi Olivier

can you please give me the structure of your table, maybee some sample
data too.
And please describe in words not in SQL your calculation.

Regards Martin

Am 25.01.2018 um 20:49 schrieb Olivier Leprêtre:
>
> Hi David,
>
> Thanks for your answer, I tried your suggestion as well as many other
> combinations, no success. Here are some of them. I just don't
> understand which syntax is required
>
> select roads,orders,(first_value(v1)
>
> over (partition by roads,segment order by
> orders)-(nth_value(v2,cast(row_number() over (partition by
> roads,*order *by orders)  as integer)) over (partition by
> roads,segment order by orders))) as result
>
> from mytable
>
> or
>
> select roads,orders,(first_value(v1)
>
> over (partition by roads,segment order by
> orders)-(nth_value(v2,row_number() over (partition by roads,*order* by
> orders)::integer)) over (partition by roads,segment order by orders)))
> as result
>
> from mytable
>
> >>syntax error near order (bold)
>
> select roads,orders,(first_value(v1)
>
> over (partition by roads,segment order by
> orders)-(nth_value(v2,row_number() over (partition by
> roads)::integer)) *over* (partition by roads,segment order by
> orders))) as result
>
> from mytable
>
> >> syntax error near over
>
> select roads,orders,(first_value(v1)
>
> over (partition by roads,segment order by
> orders)-nth_value(v2,row_number() over (partition by roads)::integer)
> over (partition by roads,segment order by orders)) as result
>
> from mytable
>
> >> window call cannot be imbricated
>
> select roads,orders,(first_value(v1)
>
> over (partition by roads,segment order by
> orders)-nth_value(v2,row_number()  over (partition by roads,segment
> order by orders)::integer)) as result
>
> from mytable
>
> >> nth_value requires an over clause
>
> select roads,orders,(first_value(v1)
>
> over (partition by roads,segment order by
> orders)-nth_value(v2,row_number()::integer) over (partition by
> roads,segment order by orders)) as result
>
> from mytable
>
> >> row_number requires an over clause
>
> *De :* David G. Johnston [mailto:david(dot)g(dot)johnston(at)gmail(dot)com]
> *Envoyé :* jeudi 25 janvier 2018 19:44
> *À :* Olivier Leprêtre <o(dot)lepretre(at)gmail(dot)com>
> *Cc :* pgsql-sql(at)lists(dot)postgresql(dot)org
> *Objet :* Re: nth_value and row_number in a partition
>
> On Thursday, January 25, 2018, Olivier Leprêtre <o(dot)lepretre(at)gmail(dot)com
> <mailto:o(dot)lepretre(at)gmail(dot)com>> wrote:
>
> nth_value(integer, bigint) doesn't exists.
>
> This is close, you just need to cast to integer.
>
> (cast(row_number() as integer)  over (partition by roads,segments
> order by orders)))
>
> You cannot separate the window function from its over clause.
>
> Cast( Row_number() over (...) as integer )
>
> Not tested...and I tend to use :: instead of cast
>
> David J.
>