Returning array of IDs as a sub-query with group-by - Mailing list pgsql-sql

From Andreas Joseph Krogh
Subject Returning array of IDs as a sub-query with group-by
Date
Msg-id 200708251710.57557.andreak@officenet.no
Whole thread Raw
Responses Re: Returning array of IDs as a sub-query with group-by  (Andreas Joseph Krogh <andreak@officenet.no>)
List pgsql-sql
Hi all.
I have the following schema:

create table item(
id serial primary key
);


create table item_log(
id serial primary key,
item_id integer not null references item(id),
price numeric NOT NULL
);


insert into item(id) values(1);
insert into item(id) values(2);
insert into item(id) values(3);
insert into item(id) values(4);

insert into item_log(item_id, price) values(1, 100);
insert into item_log(item_id, price) values(1, 100);
insert into item_log(item_id, price) values(1, 100);
insert into item_log(item_id, price) values(1, 200);
insert into item_log(item_id, price) values(1, 200);
insert into item_log(item_id, price) values(1, 200);
insert into item_log(item_id, price) values(1, 200);
insert into item_log(item_id, price) values(1, 200);
insert into item_log(item_id, price) values(1, 200);
insert into item_log(item_id, price) values(2, 200);
insert into item_log(item_id, price) values(2, 200);

Now, to get out all log-entries grouped on price with count the following
query gives me what I want

SELECT COUNT(il.price), i.id AS item_id, il.price FROM item i, item_log il
WHERE i.id = il.item_id GROUP BY il.price, i.id;
count | item_id | price
-------+---------+-------    3 |       1 |   100    6 |       1 |   200    2 |       2 |   200
(3 rows)

Now - I would like to return an ARRAY of item_log.id for each of the two rows.
The result I'm looking for would look like this:
count | item_id | price | item_id_array
-------+---------+-------+---------------    3 |       1 |   100 | {1,2,3}    6 |       1 |   200 | {4,5,6,7,8,9}    2
|      2 |   200 | {10,11} 

I tried this query which complains about an ungruoped column:

SELECT COUNT(il.price), i.id AS item_id, il.price,ARRAY(SELECT a.id FROM item_log a WHERE a.id = il.id) AS
item_id_arrayFROM item i, item_log il WHERE i.id = il.item_id GROUP BY il.price, i.id; 

ERROR:  subquery uses ungrouped column "il.id" from outer query

Any hints?

--
Andreas Joseph Krogh <andreak@officenet.no>
Senior Software Developer / Manager
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