Sql Hierarchy loop query

Question

This table represents a category hierarchy and the element at top of the hierarchy has the parent id as NULL. The table is as the exaple below:

**categoryId cate         


        

Answer 1

you can use recursive cte:

with cte as (
   select
      t.categoryId, t.categoryName, t.parentId,
      cast(t.categoryId as nvarchar(max)) as path
   from categories as t
   where t.categoryId = 234

   union all

   select
      c.categoryId, c.categoryName, t.parentId,
      c.path + '->' + cast(t.categoryId as nvarchar(max))
   from categories as t
       inner join cte as c on c.parentId = t.categoryId
)
select categoryid, categoryname, path + '->NULL'
from cte
where parentid is null

sql fiddle demo