MySQL的一个问题，菜鸟求教

[hhh871030]

下面这个语句错误了。。。。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  $$

错误代码： 1415
Not allowed to return a result set from a function

[rucypli]

Not allowed to return a result set from a function ORDER BY r.SortId后面加个limit 1

[ACMAIN_CHM]

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