if exists (select * from dbo.sysobjects where id = object_id(N'[tb]') and OBJECTPROPERTY(id, N'IsUserTable') = 1)
    drop table [tb]
GO

-- 示例数据
create table [tb]([id] int PRIMARY KEY,[pid] int,name nvarchar(20))
INSERT [tb] SELECT  1,0,N'中国'
UNION  ALL  SELECT  2,0,N'美国'
UNION  ALL  SELECT  3,0,N'加拿大'
UNION  ALL  SELECT  4,1,N'北京'
UNION  ALL  SELECT  5,1,N'上海'
UNION  ALL  SELECT  6,1,N'江苏'
UNION  ALL  SELECT  7,6,N'苏州'
UNION  ALL  SELECT  8,7,N'常熟'
UNION  ALL  SELECT  9,6,N'南京'
UNION  ALL  SELECT 10,6,N'无锡'
UNION  ALL  SELECT 11,2,N'纽约'
UNION  ALL  SELECT 12,2,N'旧金山'
GO

------解决方案--------------------
貌似笨狼出的面试题，呵呵