Re: limit results to one row per foreign object

[John Sidney-Woollett <johnsw(at)wardbrook(dot)com>]

Without trying it out, how about something like:

select username, maxbid
from users u, (
  select user_id, max(amount) as maxbid
  from bids
  group by user_id
  where auction_id = XXX
) as b
where u.id = b.user_id;

John


Alan Bullock wrote:
> hi all, I have the following schema:
>
> CREATE TABLE auctions ( id serial NOT NULL, user_id int4, title 
> varchar(255), body varchar(255), CONSTRAINT auctions_pkey PRIMARY KEY (id) ) 
> WITHOUT OIDS;
>
> CREATE TABLE bids ( id serial NOT NULL, auction_id int4, user_id int4, 
> amount float8, created_at timestamp, CONSTRAINT bids_pkey PRIMARY KEY (id) ) 
> WITHOUT OIDS;
>
> CREATE TABLE users ( id serial NOT NULL, username varchar(255), CONSTRAINT 
> users_pkey PRIMARY KEY (id) ) WITHOUT OIDS;
>
> I'd like to return all the bids for a given auction, but limit it to only 
> the *latest* bid from each user. so regardless of how many bids a user has 
> placed, only their latest is returned.
>
> I dont have a clue where to even start with this and would appreciate some 
> pointers
> thanks
>
> alan 
>
>
>
>
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