Re: Converting Rows to Columns

Joshua Berry <yoberi(at)gmail(dot)com> wrote:

> Greetings all,
>
> I know that this is an elementary question, so I'm just asking for a pointer in
> the right direction.
>
> I have a query like this that tries to link Retail shops (from the table
> aliased as 'a') to sales reps (from the table aliased as 'e') that service the
> given Retail shop:
>
> select a.id_pdv, e.apellido ||', ' || e.nombre as seller_name from tbl_pdvs a
> join tbl_circuitos b using (id_circuito) join tbl_frecuencias c on
> b.id_circuito = c.id_circuito join tbl_rutas d on c.id_ruta = d.id_ruta join
> tbl_vendedores e on d.vendedor = e.id_vendedor order by a.id_pdv limit 4;
>
>
> id_pdv | seller_name
> ---------+-------------------
> 1000001 | COLON, CRISTOBOL
> 1000001 | LOPEZ, CARLOS
> 1000002 | COLON, CRISTOBOL
> 1000002 | LUGO, FERNANDO
>
>
> As you can see, there are two salesmen that service this shop.
>
> What I need is to be able to create a report that has each unique id_pdv as a
> row of the result set, with three columns available to show up to three salemen
> that are assigned to the route.
>
> So this would give something like this:
>
> id_pdv | seller_name1 | seller_name2 | seller_name3
> ---------+------------------+----------------+----------------
> 1000001 | COLON, CRISTOBOL | LOPEZ, CARLOS | (\N or '')
> 1000002 | COLON, CRISTOBOL | LUGO, FERNANDO | (\N or '')

Not really your desired result, but i think, a solution:

test=# select * from joshua ;
id | name
----+-------
1 | user1
1 | user2
1 | user3
2 | user4
2 | user5
3 | user6
(6 rows)

Time: 0.138 ms
test=*# CREATE AGGREGATE array_accum (anyelement)
test-# (
test(# sfunc = array_append,
test(# stype = anyarray,
test(# initcond = '{}'
test(# );
CREATE AGGREGATE
Time: 0.503 ms
test=*# select id, array_accum(name) from joshua group by id order by
id;
id | array_accum
----+---------------------
1 | {user1,user2,user3}
2 | {user4,user5}
3 | {user6}
(3 rows)

Time: 0.369 ms
test=*#

Andreas
--
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