select b.*
from 部门 a join 员工 b on a.id = b.deptid
where a.fullpath = '01'

------解决方案--------------------
join on 就行了，
楼上已经解决

------解决方案--------------------

select a.Name 
from 人员表 a
where a.deptID=(select 部门表.ID from 部门表 where FullPath='01')

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

declare @fullpath varchar(2)

select @fullpath='01'

select b.*
from 部门 a join 员工 b on a.id = b.deptid
where a.fullpath=@fullpath