Hierarchical Queries in SQL Server 2005

This creates your typical hierarchical table and uses a CTE to select the hierarchy structure and create a path for each item.

CREATE TABLE tblHierarchy (ID int, ParentID int NULL, Name varchar(128));

INSERT INTO tblHierarchy VALUES (1, NULL, '1');
INSERT INTO tblHierarchy VALUES (2, NULL, '2');
INSERT INTO tblHierarchy VALUES (3, NULL, '3');
INSERT INTO tblHierarchy VALUES (4, 1, '1.1');
INSERT INTO tblHierarchy VALUES (5, 1, '1.2');
INSERT INTO tblHierarchy VALUES (6, 4, '1.1.1');

WITH Parent AS
(
    SELECT
        ID,
        ParentID,
        Name AS Path
    FROM
        tblHierarchy
    WHERE
        ParentID IS NULL

    UNION ALL

    SELECT
        TH.ID,
        TH.ParentID,
        CONVERT(varchar(128), Parent.Path + '/' + TH.Name) AS Path
    FROM
        tblHierarchy TH
    INNER JOIN
        Parent
    ON
        Parent.ID = TH.ParentID
)
SELECT * FROM Parent

OUTPUT:

ID  ParentID    Path
1   NULL        1
2   NULL        2
3   NULL        3
4   1       1/1.1
5   1       1/1.2
6   4       1/1.1/1.1.1

Having used both, I found CONNECT BY is somewhat more flexible and easier to use than CTE's. The question is not dissimilar to one I answered a few weeks ago. See Here for a brief comparison of CONNECT BY and CTE's and Here for an example of a query using CTE's.

Just FYI. SQL Server 2008 supports a new data type Hierarchy ID.

in SQL Server 2005 you can use Common Table Expressions (CTE) for this.