Обсуждение: join with an array

Hi,

I'm trying the following query:
select array_agg(t1.id) from table1 t1 join table2 t2 on (t2.id = any(array_agg)) group by t1.col1;

but I get this error: ERROR:  column "array_agg" does not exist

I tried aliasing array_agg(t1.id) without success.

Thanks for any suggestions,

In response to Louis-David Mitterrand :
> Hi,
> 
> I'm trying the following query:
> 
>     select array_agg(t1.id) from table1 t1 join table2 t2 on (t2.id = any(array_agg)) group by t1.col1;
> 
> but I get this error: ERROR:  column "array_agg" does not exist
> 
> I tried aliasing array_agg(t1.id) without success.
> 
> Thanks for any suggestions,

I can't really understand what you want to achieve, but maybe this is
what you are looking for:

test=*# select * from a;id | v
----+--- 1 | 1 2 | 1 3 | 1 4 | 1 5 | 2 6 | 2
(6 rows)

test=*# select * from b;id
---- 1 3
(2 rows)

test=*# select array_agg(a.id), v from a join b on (b.id in (select a.id from a)) group by a.v;    array_agg     | v
-------------------+---{1,2,3,4,1,2,3,4} | 1{6,5,5,6}         | 2
(2 rows)



Question: you are 'pif' in the irc-channel?


Regards, Andreas
-- 
Andreas Kretschmer
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On Wed, Feb 24, 2010 at 02:09:09PM +0100, A. Kretschmer wrote:
> In response to Louis-David Mitterrand :
> > Hi,
> > 
> > I'm trying the following query:
> > 
> >     select array_agg(t1.id) from table1 t1 join table2 t2 on (t2.id = any(array_agg)) group by t1.col1;
> > 
> > but I get this error: ERROR:  column "array_agg" does not exist
> > 
> > I tried aliasing array_agg(t1.id) without success.
> > 
> > Thanks for any suggestions,

> I can't really understand what you want to achieve, but maybe this is
> what you are looking for:

Here is a test case I built. I want to list all cruises by cruise_type
but after merging cruise_type that have the same cruise_type_name:

drop table cruise;
drop table cruise_type;

create table cruise_type (   id_cruise_type serial primary key,   cruise_type_name text
);

create table cruise (   id_cruise serial,   id_cruise_type integer references cruise_type,   cruise_date timestamp
defaultnow()
 
);

insert into cruise_type (cruise_type_name) values 
('5 day eastern carribean cruise'),
('5 day western carribean cruise'),
('5 day eastern carribean cruise'),
('5 day western carribean cruise')
;

insert into cruise (id_cruise_type) values 
(1),
(2),
(3),
(4),
(1),
(2),
(3),
(4)
;

select array_agg(ct.id_cruise_type),ct.cruise_type_name from cruise_type ct join cruise c on (c.id_cruise =
any(array_agg))group by cruise_type_name;
 

Στις Wednesday 24 February 2010 15:34:48 ο/η Louis-David Mitterrand έγραψε:

> Here is a test case I built. I want to list all cruises by cruise_type
> but after merging cruise_type that have the same cruise_type_name:
>
> drop table cruise;
> drop table cruise_type;
>
> create table cruise_type (
>     id_cruise_type serial primary key,
>     cruise_type_name text
> );
>
> create table cruise (
>     id_cruise serial,
>     id_cruise_type integer references cruise_type,
>     cruise_date timestamp default now()
> );
>
> insert into cruise_type (cruise_type_name) values
> ('5 day eastern carribean cruise'),
> ('5 day western carribean cruise'),
> ('5 day eastern carribean cruise'),
> ('5 day western carribean cruise')
> ;
>
> insert into cruise (id_cruise_type) values
> (1),
> (2),
> (3),
> (4),
> (1),
> (2),
> (3),
> (4)
> ;
>
> select array_agg(ct.id_cruise_type),ct.cruise_type_name from cruise_type ct join cruise c on (c.id_cruise =
any(array_agg))group by cruise_type_name; 
>

You dont specify (in english) what you exactly want to achive, but here is my shot:
1st, get the cruises by cruise type:
select ct.id_cruise_type,array_agg(c.id_cruise) as "List of Cruises" from cruise_type ct, cruise c WHERE
c.id_cruise_type=ct.id_cruise_typeGROUP BY ct.id_cruise_type ORDER BY ct.id_cruise_type;id_cruise_type | List of
Cruises
----------------+-----------------             1 | {1,5}             2 | {2,6}             3 | {3,7}             4 |
{4,8}
(4 rows)

test=#
Then you may pretify this to include the name of each cruise type as well:

select ct.id_cruise_type,ct.cruise_type_name,array_agg(c.id_cruise) as "List of Cruises" from cruise_type ct, cruise c
WHEREc.id_cruise_type=ct.id_cruise_type GROUP BY ct.id_cruise_type,ct.cruise_type_name ORDER BY
ct.id_cruise_type;id_cruise_type|        cruise_type_name        | List of Cruises 
----------------+--------------------------------+-----------------             1 | 5 day eastern carribean cruise |
{1,5}            2 | 5 day western carribean cruise | {2,6}             3 | 5 day eastern carribean cruise | {3,7}
      4 | 5 day western carribean cruise | {4,8} 
(4 rows)

EXERCISE:
Why cant we exclude ct.id_cruise_type from the select clause and group by of the above query?

--
Achilleas Mantzios