ALTER FUNCTION [dbo].[GetBranch]
(   
    @ac_id int
)
RETURNS TABLE
AS
RETURN
(
    WITH cte (ac_id) AS
    (


        SELECT ac_id
        FROM ArticleClass
        WHERE ac_id = @ac_id

        UNION ALL
        SELECT a.ac_id
        FROM ArticleClass a
             INNER JOIN cte c
             ON a.parent_id = c.ac_id
        
    )
    SELECT ac_id FROM cte
)

多谢。