mysql实现sequence功能的代码

CREATE TABLE `sys_sequence` ( `seq_name` varchar(50) CHARACTER SET latin1 COLLATE latin1_bin NOT NULL, `min_value` int(11) NOT NULL, `max_value` int(11) NOT NULL, `current_value` int(11) NOT NULL, `increment_value` int(11) NOT NULL DEFAULT '1', PRIMARY KEY (`seq_name`)) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_bin;

DELIMITER $$CREATE DEFINER=`root`@`%` FUNCTION `_nextval`(name varchar(50)) RETURNS int(11)begin declare _cur int;declare _maxvalue int; -- 接收最大值declare _increment int; -- 接收增长步数set _increment = (select increment_value from sys_sequence where seq_name = name);set _maxvalue = (select max_value from sys_sequence where seq_name = name);set _cur = (select current_value from sys_sequence where seq_name = name); update sys_sequence           -- 更新当前值set current_value = _cur + increment_value where seq_name = name ; if(_cur + _increment >= _maxvalue) then -- 判断是都达到最大值   update sys_sequence     set current_value = min_value     where seq_name = name ;end if;return _cur; end$$DELIMITER ;

INSERT INTO `mydb`.`sys_sequence`(`seq_name`,`min_value`,`max_value`,`current_value`,`increment_value`)VALUES('seq_name1', 1, 99999999, 1, 1);

select _nextval('seq_name1');