SQL query to get full hierarchy path

Question

I have a table with three columns NodeId, ParentNodeId, NodeName. for each node I would like to get a full path like "lvl1/lvl2/lvl3..." where lvl1,lvl2 and lvl3 are node names. I found a function which does that at this link http://www.sql-server-helper.com/functions/get-tree-path.aspx. but I would like to use CTE OR any other technique for efficiency. Please let me know if it is possible to achieve this in a better way. Thanks in advance.

Answer 1

Here's a CTE version.

declare @MyTable table (
    NodeId int,
    ParentNodeId int,
    NodeName char(4)
)

insert into @MyTable
    (NodeId, ParentNodeId, NodeName)
    select 1, null, 'Lvl1' union all
    select 2, 1, 'Lvl2' union all
    select 3, 2, 'Lvl3'

declare @MyPath varchar(100)

;with cteLevels as (
    select t.NodeId, t.ParentNodeId, t.NodeName, 1 as level
        from @MyTable t
        where t.ParentNodeId is null
    union all
    select t.NodeId, t.ParentNodeId, t.NodeName, c.level+1 as level
        from @MyTable t
            inner join cteLevels c
                on t.ParentNodeId = c.NodeId
)
select @MyPath = case when @MyPath is null then NodeName else @MyPath + '/' + NodeName end
    from cteLevels
    order by level

select @MyPath

Answer 2

I solved it like this, much similar to Joe's solution.

    with cte (NodeId,NodeName,hierarchyPath)as
(
    select NodeId,NodeName, NodeName
    from Node
    where ParentNodeId is null 
    union all
    select n.NodeId, n.NodeName, CONVERT(varchar(256), cte.hierarchyPath + '/' + n.NodeName)
    from Node n
    join cte on n.ParentNodeId = cte.NodeId
)

select * 
from cte 
order by NodeId