Postgres - bind results of equal type by year - long to wide data - postgresql

Question

Please excuse my not very propper way of asking this as i am new to postgres...
Having the following two tables:
CREATE TABLE pub (
id int
, time timestamp
);
id time
1 1 2010-02-10 01:00:00
2 2 2011-02-10 01:00:00
3 3 2012-02-10 01:00:00
And
CREATE TABLE val (
id int
, type text
, val int
);
id type val
1 1 A 1
2 1 B 2
3 1 C 3
4 2 A 4
5 2 B 5
6 3 D 6
I would like to get the following output (for id <= 2 )
type 2010 2011
1 A 1 4
2 B 2 5
3 C 3 NULL
So type is the superset of all type's present in table val.
NULL meaning that there is no value for label C.
Ideally the column-headings are are years of the time. Alternatively the id itself...

Answer 1

Exists at least two ways to do this.
If your table have not many categories you can use CTE
WITH x AS (
SELECT type,
sum(val) FILTER (WHERE date_part('year', time) = 2010) AS "2010",
sum(val) FILTER (WHERE date_part('year', time) = 2011) AS "2011"
FROM pub AS p JOIN val AS v ON (v.id = p.id)
GROUP BY type
)
SELECT * FROM x
WHERE "2010" is NOT NULL OR "2011" IS NOT NULL
ORDER BY type
;
But if you have many or dynamic categories you must use crosstab:
CREATE EXTENSION tablefunc;
SELECT * FROM crosstab(
$$
SELECT type,
date_part('year', time)::text as time,
sum(val) AS val
FROM pub AS p JOIN val AS v ON (v.id = p.id)
GROUP BY type, 2
ORDER BY 1, 2
$$,
$$VALUES ('2010'::text), ('2011'), ('2012') $$
) AS ct (type text, "2010" int, "2011" int, "2012" int);
;