mysql - 如何使用 join 到 mysql 函数中

Question

我有一个函数如下:

DELIMITER $$
DROP FUNCTION IF EXISTS `vmtest`.`hello2`$$
CREATE DEFINER = `root`@`localhost` FUNCTION `vmtest`.`hello2` (s CHAR(20)) 
RETURNS TEXT
BEGIN 
    DECLARE RETURNID INTEGER;
    DECLARE RETURNNAME TEXT;
    DECLARE PARENTID INTEGER;
    DECLARE RTN TEXT;
    DECLARE RTNNAME TEXT;
    SET RTN = "";
    SET PARENTID = s;

    WHILE PARENTID > 0 DO
        SELECT 
        t1.category_parent_id INTO RETURNID,
        t2.category_name INTO RETURNNAME  
  FROM e255g_virtuemart_category_categories AS t1
        INNER JOIN e255g_virtuemart_categories_de_de AS t2 on t1.id = t2.virtuemart_category_id
        WHERE t1.id = PARENTID;
        IF RETURNID >0 THEN
            IF RTN ="" THEN
                SET RTN = RETURNID;
            ELSE
                SET RTN = CONCAT(RTN, ',', RETURNID);
                SET RETURNNAME = CONCAT(RTNNAME, ',', RETURNNAME);
            END IF;
        END IF;
        SET PARENTID = RETURNID;            
    END WHILE;
    RETURN RETURNNAME;
END$$

DELIMITER ;

我尝试在函数中使用联接查询，但它给了我错误，如下所示:

Error in query (1327): Undeclared variable: t2

请帮忙

Answer 1

它对多个 INTO 变量有点敏感。它只是:

DELIMITER $$
DROP FUNCTION IF EXISTS `vmtest`.`hello2`$$
CREATE DEFINER = `root`@`localhost` FUNCTION `vmtest`.`hello2` (s CHAR(20)) 
RETURNS TEXT
BEGIN 
    DECLARE RETURNID INTEGER;
    DECLARE RETURNNAME TEXT;
    DECLARE PARENTID INTEGER;
    DECLARE RTN TEXT;
    DECLARE RTNNAME TEXT;
    SET RTN = "";
    SET PARENTID = s;

    WHILE PARENTID > 0 DO
        SELECT 
        t1.category_parent_id,t2.category_name INTO RETURNID,RETURNNAME  
        FROM e255g_virtuemart_category_categories AS t1
        INNER JOIN e255g_virtuemart_categories_de_de AS t2 
        on t1.id = t2.virtuemart_category_id
        WHERE t1.id = PARENTID;
        IF RETURNID >0 THEN
            IF RTN ="" THEN
                SET RTN = RETURNID;
            ELSE
                SET RTN = CONCAT(RTN, ',', RETURNID);
                SET RETURNNAME = CONCAT(RTNNAME, ',', RETURNNAME);
            END IF;
        END IF;
        SET PARENTID = RETURNID;            
    END WHILE;
    RETURN RETURNNAME;
END$$

DELIMITER ; 

所以它是...INTO var1,var2,...