带有子查询的这个FULL OUTER JOIN有什么问题？

Question

SELECT * 
  FROM 
     ( SELECT * 
         FROM tb_emp_activity_details
            , tb_activity_types
        WHERE act_type_related_id = activity_type_id 
          AND emp_act_org_id = 1 
          AND emp_related_id = 1
     ) tabone 
  FULL 
 OUTER 
  JOIN 
     ( SELECT * 
         FROM tb_emp_effort_details
            , tb_effort_types  
        WHERE eff_type_related_id = effort_type_id 
          AND emp_eff_org_id = 1 
          AND emp_related_id = 1
     ) tabtwo 
    ON tabone.startDate = tabtwo.startDate 
 ORDER 
    BY tabone.startDate
     , tabtwo.startDate;

有人可以指出我在这个查询中做错了什么吗？它的方法是检查FULL OUTER JOIN附近的SQL语法。

感谢。