MySQL:为什么这样的小改动会造成存储过程错误呢？

 DELIMITER $$                  
USE mysql$$
DROP PROCEDURE IF EXISTS demo$$
CREATE PROCEDURE demo(_id INT, _content VARCHAR(64))    
BEGIN              
    SET @id = _id;
    SET @content = _content;
                                                                                      
    PREPARE stmt FROM "INSERT INTO blog (id, content) VALUES(?, ?)";
    EXECUTE stmt USING @id, @content;
    DEALLOCATE PREPARE stmt;
END$$
DELIMITER ;
DELIMITER $$

如果改写成如下就会报错：

 DELIMITER $$

USE mysql$$
DROP PROCEDURE IF EXISTS demo$$
CREATE PROCEDURE demo(_id INT, _content VARCHAR(64))    
BEGIN              
    -- set @id = _id;
    -- set @content = _content;

    PREPARE stmt FROM "INSERT INTO blog (id, content) VALUES(?, ?)";
    EXECUTE stmt USING _id, _content;
    DEALLOCATE PREPARE stmt;
END$$
DELIMITER ;

 错误代码： 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 '_id, _content;
    DEALLOCATE PREPARE stmt;
END' at line 7