MySQL的一个问题，菜鸟求教

   DELIMITER $$

CREATE FUNCTION GetKnowledgeSortIdByKLId

(

	ObjectId INT,

	TYPE INT 

)

RETURNS NVARCHAR(4000)



    BEGIN 



        DECLARE str NVARCHAR(4000); 

        SET str = '' ;

        

        SELECT  str = str + ',' + CAST(r.SortId AS CHAR(10))

        FROM    dbo.KL_Re_Knowledge_Sort r

        LEFT JOIN KL_KnowledgeSort ON KL_KnowledgeSort.SortId= r.SortId

        WHERE r.ObjectId=ObjectId AND r.Type=TYPE AND KL_KnowledgeSort.IsDelete=0

        ORDER BY r.SortId;

          

        IF ( LENGTH(str) > 1 ) THEN

            

                SET str = RIGHT(str, LENGTH(str) - 1) ;

		END IF;

        RETURN(str);

    END  $$