mysql:第1行的DELIMITER语法错误

我尝试在phpmyadmin/MySQL中使用以下SQL添加此函数

DROP FUNCTION IF EXISTS `__myv`;
DELIMITER ;;
CREATE   FUNCTION `__myv`(`a` int, `b` int) RETURNS bigint(20)
BEGIN

    return FLOOR(a / b);
END;;
DELIMITER ;

但我得到这个错误:

错误

SQL query:

DELIMITER;

MySQL said: Documentation
#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 'DELIMITER' at line 1 

如何解决这个错误？