How to Limit CTE Recursion Depth but Select Generic Table?

Question

Currently we have a stored procedure that returns data from a table in it\'s original schema by doing something like this:

WITH CTE AS
(
    -- Start CTE off         


        

Answer 1

If all you want to do with your level field is limit the number of recursions, you should be able to use a MAXRECURSION query hint, something like this:

WITH Department_CTE AS
(
    SELECT
        DepartmentGroupKey,
        ParentDepartmentGroupKey,
        DepartmentGroupName
    FROM dimDepartmentGroup
    WHERE DepartmentGroupKey = 2
    UNION ALL
    SELECT
        Child.DepartmentGroupKey,
        Child.ParentDepartmentGroupKey,
        Child.DepartmentGroupName
    FROM Department_CTE AS Parent
        JOIN DimDepartmentGroup AS Child
            ON Parent.ParentDepartmentGroupKey = Child.DepartmentGroupKey
)
SELECT * FROM Department_CTE
OPTION (MAXRECURSION 2)

Edit:

In answer to the question in the comments, no, you can't suppress the error that you get when recursing more times than your MAXRECURSION setting allows. If I understand you correctly, you could do something like this:

WITH CTE AS
(
    -- Start CTE off by selecting the task that was provided to stored procedure.
    SELECT Id, 0 as [Level]
    FROM [dbo].[TestTable]
    WHERE [Id] = 1
    -- Recursively add tasks that are children of parent tasks that have already been found in previous iterations.
    UNION ALL
    SELECT t.Id, [Level] + 1
    FROM [dbo].[TestTable] as t
    INNER JOIN CTE as tcte
        ON t.[ParentId] = tcte.[Id]
    WHERE [Level] < 2
),
CTE2 AS
(
    SELECT TestTable.*
    FROM CTE
        INNER JOIN TestTable ON CTE.Id = TestTable.Id
)
SELECT * FROM CTE2;

This should be equally as generic as what you have above, assuming you're not planning on changing the hierarchical or primary key fields.