mysql - 在mysql中使用select into局部变量和准备好的语句

Question

每次调用这个存储过程我都会得到这个错误:

#1064 - You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'NULL' at line 1

似乎是什么问题？

代码如下:

DELIMITER $$

DROP PROCEDURE IF EXISTS `singledb`.`TOUR_TRANSFER`$$

CREATE DEFINER=`root`@`localhost` PROCEDURE `TOUR_TRANSFER`()
BEGIN

BEGIN -- for rubric table
            DECLARE tblRubric_rubric_id INT;
            SET @qry = concat('SELECT count(*) into ',tblRubric_rubric_id,' FROM zerodb2.tour_template');
            PREPARE statement FROM @qry;
            EXECUTE statement;

            SELECT tblRubric_rubric_id;
END;
END$$

DELIMITER ;

Answer 1

来自 http://bugs.mysql.com/bug.php?id=15263 :

"Parameter markers can be used only where data values should appear, not for SQL keywords, identifiers, and so forth."

所以，我们不能这样做:

PREPARE stmt FROM 'SELECT id INTO ? FROM t1';

我们不能用?代替标识符(变量名)。

当你使用参数名时:

PREPARE stmt FROM 'SELECT id INTO rid FROM t1';

在正在准备的字符串中，服务器根本不知道 rid 在您尝试准备的语句中指的是什么。您可以尝试在 SP 之外准备它，结果相同:

mysql> prepare stmt from 'select id into p from t1';
ERROR 1327 (42000): Undeclared variable: p

所以我只使用了用户变量，见下文:

DROP PROCEDURE IF EXISTS `singledb`.`TOUR_TRANSFER`$$

CREATE DEFINER=`root`@`localhost` PROCEDURE `TOUR_TRANSFER`()
BEGIN
  BEGIN -- for rubric table
    -- DECLARE @tblRubric_rubric_id INT;

    SET @tblRubric_rubric_id := 0;
    SET @qry = 'SELECT count(*) into @tblRubric_rubric_id FROM zerodb2.tour_template';
    PREPARE statement FROM @qry;
    EXECUTE statement;
  END;
END$$