众所周知，日期/时间函数依赖于数据库。不过，以下是一种典型的方法：

select yyyy, mm, sum(num_ordered), sum(num_shipped)
from ((select year(ordered) as yyyy, month(ordered) as mm, count(*) as num_ordered, 0 as num_shipped
       from orders
       group by year(ordered), month(ordered)
      ) union all
      (select year(shipped) as yyyy, month(shipped) as mm, 0 count(*) as num_shipped
       from orders
       group by year(shipped), month(shipped)
      ) 
     ) ym
group by yyyy, mm;