您可以使用公用表表达式.

WITH LeveledSiteMap(Id, Name, Level)
AS
(
    SELECT Id, Name, 1 AS Level
    FROM MySiteMap
    WHERE Parent_Id IS NULL
    UNION ALL
    SELECT m.Id, m.Name, l.Level + 1
    FROM MySiteMap AS m
        INNER JOIN LeveledSiteMap AS l
        ON m.Parent_Id = l.Id
)
SELECT *
FROM LeveledSiteMap