union来合并两个表的列

create or replace view treeview as select a.area_id par_Id, 0 men_Id, a.area_name men_Name from area a union select d.area_id, d.department_id , d.department_name from department d

注意两个表的字段在查询中对应，要有相同的数据类型。

如下图结果