受到其他答案的启发，但组织起来可能更好：
SELECt *, brcht + cana + font + nr AS total FROM (SELECt insee, annee, SUM(Coalesce(brcht.nb, 0)) brcht, SUM(Coalesce(cana.nb, 0)) cana, SUM(Coalesce(font.nb, 0)) font, SUM(Coalesce(nr.nb, 0)) nr FROM brcht full outer join cana USING (insee, annee) full outer join font USING (insee, annee) full outer join nr USING (insee, annee) GROUP BY insee, annee) t ORDER BY insee,annee;
给予：
insee | annee | brcht | cana | font | nr | total --------+-------+-------+------+------+----+------- 036223 | 2013 | 0 | 0 | 0 | 1 | 1 036223 | 2014 | 0 | 0 | 0 | 1 | 1 036223 | 2017 | 0 | 1 | 0 | 0 | 1 086001 | 2013 | 0 | 0 | 0 | 1 | 1 086001 | 2014 | 0 | 0 | 0 | 2 | 2 086001 | 2015 | 0 | 0 | 0 | 4 | 4 086001 | 2016 | 0 | 2 | 0 | 2 | 4(7 rows)
