Cara unpivot tabel di PostgreSQL

PostgreSQL 9.3 menawarkan fungsi JSON rapi yang dapat digunakan untuk tugas-tugas tersebut tanpa mendefinisikan fungsi baru atau mengetahui sejumlah kolom.

SELECT id, (k).key as year, (k).value as value FROM
  (SELECT j->>'id' as id, json_each_text(j) as k
    FROM (
       SELECT row_to_json(tbl) as j FROM tbl) 
    as q)
    as r
WHERE (k).key <> 'id';

http://sqlfiddle.com/#!15/1714b/13