假设你想得到一个单一的金额每年，这里有一个选择使用 union all :

SELECT year, SUM(scost) scostsum, 
FROM (
  SELECT syear as year, scost as cost from table1 
  UNION ALL
  SELECT hyear as year, hcost as cost from table2 
  ) t
GROUP by year;

根据您的评论，如果您想要多个总和，您必须创建一个年份表，然后使用 outer joins 得到你的成本和成本。举个例子：

select year, coalesce(s.cost,0) as scost, coalesce(h.cost,0) as hcost
from (select syear as year from table1 union select hyear from table2) years
    left join (
      select syear, sum(scost) cost
      from table1 
      group by syear) s on years.year = s.syear
    left join (
      select hyear, sum(hcost) cost
      from table2 
      group by hyear) h on years.year = h.hyear