mysql实现sequence功能的代码_Mysql_

 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');