sql 列集合转换成逗号分隔的字符类型

CREATE function [dbo].[getGroupPath](@groupId int)
returns nvarchar(2000)
as
begin
declare @path nvarchar(2000)='/';
with cr as
(
select * from FAQGroup where Id=@groupId
union all
select b.* from cr a join FAQGroup b on a.ParentId=b.id
)
select @path=@path+cast(ID as nvarchar) +'/'     from cr order by id  

return left(@path,len(@path))