Re: Inline count on a query

On Wednesday, August 19, 2020, Laura Smith <
n5d9xq3ti233xiyif2vp(at)protonmail(dot)ch> wrote:

> Hi,
>
> Let's say we've got a fairly basic table :
>
> create table networks (
> lan_id text not null,
> net_id text not null,
> port_id text not null
> );
> create index net_uniq on networks(lan_id,port_id);
>
> The query conundrum I am facing is that I need to add metadata to the
> output of the query that indicates the count of ports a given net has on a
> lan.
>
> So, for example, given :
> insert into networks(lan_id,net_id,port_id) values('L1','N1,'P1');
> insert into networks(lan_id,net_id,port_id) values('L1','N1,'P2');
>
> The metadata count would be 1, 2 (because 'N1' has 'P1' and 'P2' on 'L1').
>
> Is there a sensible way to query this without stressing out Postgres too
> much ? I'm guessing a CTE of some sort ?
>
>
Suggest you provide your desired output in table format, and show “the
query” that you mention.

David J.