SQL Split - insert into hierarchical table structure - sql

Question

I'm using a Split function (found on social.msdn.com) and when executing manually in a query window
SELECT * FROM dbo.Split('/ABC/DEF/GHI/JKL', '/')
I get the following
Id Name
-- ----
1
2 ABC
3 DEF
4 GHI
5 JKL
Where Id is just a sequential number indicating position within the original string and Name is the name of that node. No hierarchical information yet.
Now, the next step is to put this into a hierarchical data structure in the DB. I'm trying to do this in a stored proc and with my SQL skills being what they are, I've hit a wall. Here's what I'd like to have: (NOTE that the Id column above is not related to the Id or the ParentId column here.)
Id ParentId Name FullName
-- -------- ---- --------
1 NULL ABC /ABC
2 1 DEF /ABC/DEF
3 2 GHI /ABC/DEF/GHI
4 3 JKL /ABC/DEF/GHI/JKL
I've got this far with my SP (called GetId with param #FullName) - GetId should return the Id associated with this node. If the node doesn't exist, it should be created and the Id from that new row should be returned - in other words, the consumer of this SP shouldn't care or know if the node exists prior to its calling it:
DECLARE #count int
-- // is there already a row for this node?
SELECT #count = COUNT(CatId)
FROM Category
WHERE FullName = #FullName
-- // if no row for this node, create the row
-- // and perhaps create multiple rows in hierarchy up to root
IF (#count = 0)
BEGIN
SELECT * FROM Split(#FullName, '/')
-- // NOW WHAT ???
-- // need to insert row (and perhaps parents up to root)
END
-- // at this point, there should be a row for this node
-- // return the Id associated with this node
SELECT Id
FROM Category
WHERE FullName = #FullName
The Category table (adjacency list) where these items will eventually end up, through a series of inserts, has the following structure.
CREATE TABLE Category (
Id int IDENTITY(1,1) NOT NULL PRIMARY KEY,
ParentId int NULL,
Name nvarchar(255) NOT NULL,
FullName nvarchar(255) NOT NULL)
As result, I do not want to generate a value for the Id column in the Category table and need to get the appropriate ParentId for each node.
After the paths '/ABC/DEF/GHI/JKL' and '/ABC/DEF/XYZ/LMN/OPQ' were processed and I did a SELECT * FROM Category, I would expect to see the following:
Id ParentId Name FullName
-- -------- ---- --------
1 NULL ABC /ABC
2 1 DEF /ABC/DEF
3 2 GHI /ABC/DEF/GHI
4 3 JKL /ABC/DEF/GHI
5 2 XYZ /ABC/DEF/XYZ
6 5 LMN /ABC/DEF/XYZ/LMN
7 6 OPQ /ABC/DEF/XYZ/LMN/OPQ
Q: would it be possible to call back into the SP recursively starting at the outer most node, until the node existed or we were at the ultimate parent? Something to the effect of:
GetId(#FullName)
{
If Category exists with #FullName
return CatId
Else // row doesn't exist for this node
Split #FullName, order by Id DESC so we get the leaf node first
Create Category row
#FullName,
#Name,
#ParentId = Id of next FullName (call GetId with FullName of next row from Split)
}

Answer 1

You can use CTE to achieve this, in combination with RowNumbering
With TMP AS (
SELECT Id, Data as Name, RN=ROW_NUMBER() over (Order by Id ASC)
FROM dbo.Split('/ABC/DEF/GHI/JKL', '/')
where Data > ''
), TMP2 AS (
SELECT TOP 1 RN, CONVERT(bigint, null) ParentId, Name, convert(nvarchar(max),'/' + Name) FullName
From TMP
Order by RN
union all
SELECT n.RN, t.RN, n.Name, t.FullName + '/' + n.Name
from TMP2 t
inner join TMP n on n.RN = t.RN+1)
select *
from tmp2
order by RN
Now for the 2nd part, this inserts the entire hierarchy, but starts with ID=1
IF (#count = 0)
BEGIN
With TMP AS (
SELECT Id, Data as Name, RN=ROW_NUMBER() over (Order by Id ASC)
FROM dbo.Split('/ABC/DEF/GHI/JKL', '/')
where Data > ''
), TMP2 AS (
SELECT TOP 1 RN, CONVERT(bigint, null) ParentId, Name, convert(nvarchar(max),'/' + Name) FullName
From TMP
Order by RN
union all
SELECT n.RN, t.RN, n.Name, t.FullName + '/' + n.Name
from TMP2 t
inner join TMP n on n.RN = t.RN+1)
insert Category(CatId, ParentId, Name, FullName) --<< list correct column names
select RN, ParentId, Name, FullName
from tmp2
order by RN
END