Re: nth_value and row_number in a partition

Hi

I think you can do this without any need to use nth_value.
Only first_value and current v2 is needed.

select roads, orders, v1, v2, segment,
first_value(v1) over(partition by roads, segment order by roads, orders) 
- v2
from test order by roads, orders;

The point is to define the partition by roads and segment but to order 
it via roads and orders.


Regards Martin

Am 25.01.2018 um 21:52 schrieb Olivier Leprêtre:
>
> Hi Martin,
>
> Here is an example in a "excel view". Red value are first value. 3 
> partitions defined by roads and segment columns.
>
> The goal is to substract v2 (D) from v1 first value for each window. 
> Hope this is clear enough.
>
> Davir, you're right, imbricated is my bad translation for nested.
>
>
> 	
>
> A
>
> 	
>
> B
>
> 	
>
> C
>
> 	
>
> D
>
> 	
>
> E
>
> 	
>
> F
>
> 	
>
> 1
>
> 	
>
> roads
>
> 	
>
> orders
>
> 	
>
> v1
>
> 	
>
> v2
>
> 	
>
> v3
>
> 	
>
> segment
>
> 	
>
> v3 calculation
>
> 2
>
> 	
>
> 41
>
> 	
>
> 1
>
> 	
>
> 632
>
> 	
>
> 0
>
> 	
>
> 632
>
> 	
>
> 1055
>
> 	
>
> C2-D2
>
> 3
>
> 	
>
> 41
>
> 	
>
> 2
>
> 	
>
> 632
>
> 	
>
> 0
>
> 	
>
> 632
>
> 	
>
> 1055
>
> 	
>
> C2-D3
>
> 4
>
> 	
>
> 41
>
> 	
>
> 3
>
> 	
>
> 600
>
> 	
>
> 16
>
> 	
>
> 616
>
> 	
>
> 1055
>
> 	
>
> C2-D4
>
> 5
>
> 	
>
> 41
>
> 	
>
> 4
>
> 	
>
> 70
>
> 	
>
> 25
>
> 	
>
> 607
>
> 	
>
> 1055
>
> 	
>
> C2-D5
>
> 6
>
> 	
>
> 41
>
> 	
>
> 5
>
> 	
>
> 60
>
> 	
>
> 30
>
> 	
>
> 30
>
> 	
>
> 1041
>
> 	
>
> C6-D6
>
> 7
>
> 	
>
> 41
>
> 	
>
> 6
>
> 	
>
> 64
>
> 	
>
> 3
>
> 	
>
> 57
>
> 	
>
> 1041
>
> 	
>
> C6-D7
>
> 8
>
> 	
>
> 41
>
> 	
>
> 7
>
> 	
>
> 14
>
> 	
>
> 2
>
> 	
>
> 12
>
> 	
>
> 1042
>
> 	
>
> C8-D8
>
> 9
>
> 	
>
> 41
>
> 	
>
> 8
>
> 	
>
> 2
>
> 	
>
> 6
>
> 	
>
> 8
>
> 	
>
> 1042
>
> 	
>
> C8-D9
>
> Thanks very much for your help
>
> *De :*Martin Stöcker [mailto:[email protected]]
> *Envoyé :* jeudi 25 janvier 2018 21:13
> *À :* Olivier Leprêtre <[email protected]>; 
> [email protected]
> *Objet :* 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:[email protected]]
>     *Envoyé :* jeudi 25 janvier 2018 19:44
>     *À :* Olivier Leprêtre <[email protected]>
>     <mailto:[email protected]>
>     *Cc :* [email protected]
>     <mailto:[email protected]>
>     *Objet :* Re: nth_value and row_number in a partition
>
>     On Thursday, January 25, 2018, Olivier Leprêtre
>     <[email protected] <mailto:[email protected]>> 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.
>

-- 
Widdersdorfer Str. 415, 50933 Köln; Tel. +49 / 221 / 9544 010
HRB Köln HRB 75439, Geschäftsführer: S. Böhland, S. Rosenbauer