Get more than 1 result set for recursive CTE? - sql-server

Question

I have a simple table which has leafs and sub leafs info. ( like a forum questions)
A main message is defined where childId and ParentID are the same
So here we see 2 main questions and their answers.
I've also managed to calc the depth of each element :
In short this is the main query :
WITH CTE AS
(
SELECT childID
,parentID,
0 AS depth,name
FROM #myTable
WHERE childID = parentID AND childID=1 -- problem line
UNION ALL
SELECT TBL.childID
,TBL.parentID,
CTE.depth + 1 , TBL.name
FROM #myTable AS TBL
INNER JOIN CTE ON TBL.parentID = CTE.childID
WHERE TBL.childID<>TBL.parentID
)
SELECT childID,parentID,REPLICATE('----', depth) + name
But the problem is Line #8 (commented).
I currently ask "give me all the cluster for question id #1"
So where is the problem ?
I want to have multiple result set , for each question !
so here i need to have 2 result sets :
one for childId=parentId=1
and one for
one for childId=parentId=6
full working sql online
(and I dont want to use cursor)

Answer 1

You can build your queries dynamically.
DECLARE #SQL NVARCHAR(MAX) =
(SELECT '
WITH CTE AS
(
SELECT childID
,parentID,
0 AS depth,name
FROM myTable
WHERE childID = parentID AND childID = '+CAST(childID AS NVARCHAR(10))+'
UNION ALL
SELECT TBL.childID
,TBL.parentID,
CTE.depth + 1 , TBL.name
FROM myTable AS TBL
INNER JOIN CTE ON TBL.parentID = CTE.childID
WHERE TBL.childID<>TBL.parentID
)
SELECT childID,parentID,REPLICATE(''----'', depth) + name
FROM CTE
ORDER BY
childID;'
FROM myTable
WHERE childID = parentID
FOR XML PATH(''), TYPE).value('text()[1]', 'NVARCHAR(MAX)');
EXEC sp_executesql #SQL;
Update:
As suggested by Bogdan Sahlean we can minimize compilations by making the actual query parameterized.
DECLARE #SQL1 NVARCHAR(MAX) =
'WITH CTE AS
(
SELECT childID
,parentID,
0 AS depth,name
FROM myTable
WHERE childID = parentID AND childID = #childID
UNION ALL
SELECT TBL.childID
,TBL.parentID,
CTE.depth + 1 , TBL.name
FROM myTable AS TBL
INNER JOIN CTE ON TBL.parentID = CTE.childID
WHERE TBL.childID<>TBL.parentID
)
SELECT childID,parentID,REPLICATE(''----'', depth) + name
FROM CTE
ORDER BY
childID;'
DECLARE #SQL2 NVARCHAR(MAX) =
(SELECT 'exec sp_executesql #SQL, N''#childID int'', '+CAST(childID AS NVARCHAR(10))+';'
FROM myTable
WHERE childID = parentID
FOR XML PATH(''), TYPE).value('text()[1]', 'NVARCHAR(MAX)');
EXEC sp_executesql #SQL2, N'#SQL NVARCHAR(MAX)', #SQL1;

Answer 2

To present multiple result sets to your client, you're going to have to use a cursor or a while loop to perform independent SELECT operations. You can't do that from a CTE, since a CTE can only be used by exactly one subsequent query.
Now, the source of the problem has nothing to do with cursors really, but the fact that you're using an HTML repeater. Why do you need to use an HTML repeater for this? A simple DataReader can loop through all of the results from the CTE's single set, and make conditional formatting decisions based on the loop and determining when the root ID changes. So I suggest you look into solving the presentation problem a different way, rather than trying to coerce SQL Server to accommodate your presentation implementation.

Answer 3

I am not sure what you mean by "returning two result sets". Could you just have one result set, with the root question being assigned into another column? The following tweak on your query does this:
WITH CTE AS (
SELECT ChildId as WhichQuestion, childID, parentID, 0 AS depth, name
FROM #myTable
WHERE childID = parentID
UNION ALL
SELECT cte.WhichQuestion, TBL.childID, TBL.parentID, CTE.depth + 1 , TBL.name
FROM #myTable AS TBL
INNER JOIN CTE ON TBL.parentID = CTE.childID
WHERE TBL.childID <> TBL.parentID
)
SELECT WhichQuestion, childID, parentID, REPLICATE('----', depth) + name
FROM CTE
ORDER BY WhichQuestion, childID;

Answer 4

You can save in anchor part childId of root question and then access all the branch by needed Id:
WITH CTE AS (
SELECT childID as RootId
, childID
, parentID
, 0 AS depth,name
FROM #myTable
WHERE childID = parentID
UNION ALL
SELECT CTE.RootId
, TBL.childID
, TBL.parentID
, CTE.depth + 1 , TBL.name
FROM #myTable AS TBL
INNER JOIN CTE ON TBL.parentID = CTE.childID
WHERE TBL.childID<>TBL.parentID
)