LISTING 1: Expanding Hierarchies Example from SQL Server Books Online

CREATE PROCEDURE expand (@current char(20)) as
SET NOCOUNT ON
DECLARE @level int, @line char(20)
CREATE TABLE #stack (item char(20), level int)
INSERT INTO #stack VALUES (@current, 1)
SELECT @level = 1

WHILE @level > 0
BEGIN
   IF EXISTS (SELECT * FROM #stack WHERE level = @level)
      BEGIN
         SELECT @current = item
         FROM #stack
         WHERE level = @level
         SELECT @line = space(@level - 1) + @current
         PRINT @line
         DELETE FROM #stack
         WHERE level = @level
            AND item = @current
         INSERT #stack
            SELECT child, @level + 1
            FROM hierarchy
            WHERE parent = @current
         IF @@ROWCOUNT > 0
            SELECT @level = @level + 1
      END
   ELSE
      SELECT @level = @level - 1
END -- WHILE