mysql存储过程调用含out参数

CREATE DEFINER=`root`@`localhost` PROCEDURE `hovertreeTest`(
    IN `Param1` INT,
    IN `Param2` VARCHAR(50),
    OUT `Param3` INT

)
LANGUAGE SQL
NOT DETERMINISTIC
CONTAINS SQL
SQL SECURITY DEFINER
COMMENT ‘测试‘
BEGIN

select param1;
select param2;
set Param3 = 6;

END

CALL `hovertreeTest`(‘9‘, ‘hovertree‘,@hvt);
select @hvt;