SELECT x.a years,nvl(y.counts,0) counts
FROM (SELECT a
      FROM (SELECT '1980' a, '1981' b, '1982' c, '1983' d FROM dual)
      UNION ALL
      SELECT b
      FROM (SELECT '1980' a, '1981' b, '1982' c, '1983' d FROM dual)
      UNION ALL
      SELECT c
      FROM (SELECT '1980' a, '1981' b, '1982' c, '1983' d FROM dual)
      UNION ALL
      SELECT d
      FROM (SELECT '1980' a, '1981' b, '1982' c, '1983' d FROM dual)) x,
     
     (SELECT TO_CHAR(e.hiredate, 'yyyy') years, COUNT(1) counts
      FROM emp e
      WHERE TO_CHAR(e.hiredate, 'yyyy') IN ('1980', '1981', '1982', '1983')
      GROUP BY TO_CHAR(e.hiredate, 'yyyy')) y
WHERE x.a = y.years(+)
ORDER BY 1

测试结果：
1    1980    1
2    1981    10
3    1982    1
4    1983    0

------解决方案--------------------
SQL code

建这么一张表吧,用来存放需要分组的年份：
create table year(
       year date
);
1980-1-1
1981-1-1
1982-1-1
1983-1-1
1987-1-1

统计sql如下：
select 
       to_char(t1.year,'yyyy') YEAR,count(t2.empno) EMP_NUM
from year t1 left join emp t2 on to_char(t1.year,'yyyy')=to_char(t2.hiredate,'yyyy')
group by to_char(t1.year,'yyyy')
order by to_char(t1.year,'yyyy')

------解决方案--------------------
表中数据：


实测结果：