sql无限级树型查询

表结构如下：

表数据如下：

一提到无限级，很容易想到递归，使用sql 的CET语法如下

with menu(Id,Name,ParentId,Level)
as
(
select Id,Name,ParentId,0 as Level from dbo.Category where ParentId is Null
Union All 
Select A.Id,A.Name,A.ParentId,B.Level+1 from dbo.Category A inner join menu B
on A.ParentId=B.Id
)
select * from menu order by Id

　　查询结果如下图：

看到这样的结果，大失所望，继续修改查询语句

with menu(Id,Name,ParentId,Level,px,px2)
as
(
select Id,Name,ParentId,0 as Level,Id px, cast(Id as nvarchar(4000)) px2  from dbo.Category where ParentId is Null
Union All 
Select A.Id,A.Name,A.ParentId,B.Level+1 ,B.px,B.px2+ltrim(A.Id) from dbo.Category A inner join menu B
on A.ParentId=B.Id
)
select * from menu order by px,px2 

　　再看一下运行结果：