Solved

Hierarchical SQL table and finding a record's lineage

Posted on 2010-11-29
3
672 Views
Last Modified: 2012-05-10
Hello.

I have a hierarchical SQL table mimicking a directory tree structure, with fields like the following:

ID
ParentID
ItemName

where a record's ParentID is defined as the ID of the record's intended parent record.

When I preform a Select, I would like to add a column, named "Path", that contains a string representation of an item's lineage, (Eg \GrandParent\Parent\Me).  Given the ID of any item within the table, how do I design a select command to recursively build a lineage string?  I use the word "recursion" loosely -- I know that actual recursion is a resource hog.  Does anyone have a workable strategy for this?

Something like:
SELECT ID, ParentID, ItemName (...something...) as Path
FROM MyTable
WHERE ID=@ID
0
Comment
Question by:ewolsing
3 Comments
 
LVL 18

Expert Comment

by:lludden
ID: 34231954
If you are using SQL 2005 or later, you might try a recursive CTE as opposed to a recursive function.

Check this MSDN article.

http://msdn.microsoft.com/en-us/library/ms186243.aspx
0
 
LVL 58

Accepted Solution

by:
cyberkiwi earned 500 total points
ID: 34232256
A sample
create table tree (ID int, ParentID int, ItemName varchar(100))

insert tree select

1,null,'GrandParent' union all select

2,1,'Parent' union all select

3,2,'Me'

GO



create function dbo.lineage(@id int)

returns varchar(max)

as

begin

declare @path varchar(max);

with tmp as (

	select level=1, parentId,convert(varchar(max),'\'+ItemName) Path

	from tree where id=@id

	union all

	select level+1,t.parentID,'\'+t.ItemName+tmp.path

	from tmp

	inner join tree t on tmp.parentID=t.id

	)

select top(1) @path=path from tmp order by level desc

return @path

end

GO



select id, parentid, dbo.lineage(id) as path

from tree

where id=3

Open in new window

0
 

Author Closing Comment

by:ewolsing
ID: 34232734
Thank you!  That was exactly what I was looking for.  While I've done a fair amount of SQL work, I've never played with recursion before.  I appreciate the insight.
0

Featured Post

Best Practices: Disaster Recovery Testing

Besides backup, any IT division should have a disaster recovery plan. You will find a few tips below relating to the development of such a plan and to what issues one should pay special attention in the course of backup planning.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

JSON is being used more and more, besides XML, and you surely wanted to parse the data out into SQL instead of doing it in some Javascript. The below function in SQL Server can do the job for you, returning a quick table with the parsed data.
I have a large data set and a SSIS package. How can I load this file in multi threading?
This video shows how to set up a shell script to accept a positional parameter when called, pass that to a SQL script, accept the output from the statement back and then manipulate it in the Shell.
Via a live example, show how to set up a backup for SQL Server using a Maintenance Plan and how to schedule the job into SQL Server Agent.

911 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question

Need Help in Real-Time?

Connect with top rated Experts

25 Experts available now in Live!

Get 1:1 Help Now