MySQL实现序列自增

#创建序列表
DROP TABLE IF EXISTS `sequence`;
CREATE TABLE `sequence` (
  `name` varchar(50) NOT NULL COMMENT '序列名称',
  `current_value` bigint(20) NOT NULL COMMENT '序列当前值',
  `increment` int(11) NOT NULL DEFAULT '1' COMMENT '步长',
  PRIMARY KEY (`name`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 comment '序列表';


#查询序列当前值
DELIMITER $$
CREATE #DEFINER=`root`@`%` 
    FUNCTION `currval`(seq_name VARCHAR(50)) RETURNS bigint(20)
    DETERMINISTIC
BEGIN
        DECLARE value VARCHAR(20);
        SET value = 0;
        SELECT current_value INTO value 
            FROM sequence 
            WHERE name = seq_name;
        RETURN value;
END$$
DELIMITER ;


#取下一个序列号
DELIMITER $$
CREATE #DEFINER=`root`@`%` 
    FUNCTION `nextval`(seq_name VARCHAR(50)) RETURNS bigint(20)
    DETERMINISTIC
BEGIN
        UPDATE sequence
            SET current_value = current_value + increment
            WHERE name = seq_name;#更新序列号
        RETURN currval(seq_name);#取当前序列号
END$$
DELIMITER ;


#为序列赋值(初始化序列)
DELIMITER $$
CREATE #DEFINER=`root`@`%` 
    FUNCTION `setval`(seq_name VARCHAR(50), value BIGINT) RETURNS bigint(20)
    DETERMINISTIC
BEGIN
        #初始化更新
        UPDATE sequence
            SET current_value = value
            WHERE name = seq_name;
        #返回序列当前值
        RETURN currval(seq_name);
END$$
DELIMITER ;