函数会返回数据，调用函数使用 select fun(),不能使用call调用，否则提示

mysql> call myfun();ERROR 1305 (42000): PROCEDURE test.myfun does not exist

下面做一个实验

CREATE TABLE `t` (	`id` INT(11) UNSIGNED NOT NULL AUTO_INCREMENT,	`n` INT(11) UNSIGNED NULL DEFAULT '0',	PRIMARY KEY (`id`))COLLATE='utf8_general_ci'ENGINE=InnoDBAUTO_INCREMENT=5;CREATE DEFINER=`neo`@`%` FUNCTION `myfun`()	RETURNS int(11)	LANGUAGE SQL	NOT DETERMINISTIC	READS SQL DATA	SQL SECURITY DEFINER	COMMENT ''BEGIN	INSERT INTO t (n) VALUES(rand()*100);	RETURN LAST_INSERT_ID();END

mysql> select myfun();+---------+| myfun() |+---------+|       9 |+---------+1 row in set, 2 warnings (0.07 sec)

USE `netkiller`;DROP function IF EXISTS `timestamp_to_iso8601`;DELIMITER $$USE `netkiller`$$CREATE DEFINER=`neo`@`db.netkiller.cn` FUNCTION `timestamp_to_iso8601`(dt timestamp) RETURNS varchar(24) CHARSET utf8BEGIN	RETURN DATE_FORMAT( CONVERT_TZ(dt, @@session.time_zone, '+00:00')  ,'%Y-%m-%dT%T.000Z');     END$$DELIMITER ;

mysql> select timestamp_to_iso8601(current_timestamp()) as iso8601;+--------------------------+| iso8601                  |+--------------------------+| 2017-12-07T07:21:22.000Z |+--------------------------+1 row in set (0.00 sec)