mysql 模仿oracle的sequence功能

第一步：创建表

DROP TABLE IF EXISTS `seq`; 
CREATE TABLE `seq` ( 
  `id` BIGINT(11) NOT NULL AUTO_INCREMENT, 
  `name` VARCHAR(255) NOT NULL COMMENT 'sequence名称', 
  `max` BIGINT(11) NOT NULL DEFAULT '1' COMMENT '最大id', 
  `length`INT(2) NOT NULL DEFAULT '1' COMMENT '生成序列后的长度,以0补全', 
  `next` INT(2) NOT NULL DEFAULT '1' COMMENT '增长的长度', 
  `rules` VARCHAR(255) DEFAULT NULL COMMENT '规则以###max_id###做为替换', 
  PRIMARY KEY (`id`), 
  UNIQUE KEY `fk_name` (`name`) 
) ENGINE=INNODB AUTO_INCREMENT=1 DEFAULT CHARSET=utf8; 

第二步：创建function bj

引用

DROP FUNCTION IF EXISTS bj;
DELIMITER $
CREATE FUNCTION bj (seq_name VARCHAR(50))
RETURNS VARCHAR(20)
CONTAINS SQL
BEGIN
    DECLARE seq_rules VARCHAR(255);
    DECLARE seq_length INT(2);
    DECLARE seq_max BIGINT(20);
  
    DECLARE max_id_length INT(20);
    DECLARE max_id VARCHAR(20);
  
    SELECT rules,seq.`length`,`max` INTO seq_rules, seq_length,seq_max FROM seq WHERE NAME = seq_name ;
  
    SET max_id = seq_max;
    SET max_id_length = CHARACTER_LENGTH(max_id);
  
    #长度不够补0
    WHILE seq_length > max_id_length DO
        SET max_id = CONCAT('0',max_id);
        SET max_id_length = CHARACTER_LENGTH(max_id);
    END WHILE;
  
    #替换规则
    IF seq_rules IS NOT NULL AND INSTR(seq_rules,'###max_id###') > 0 THEN
        SET max_id = REPLACE(seq_rules,'###max_id###',max_id);
    END IF;
  
    RETURN max_id;
END$
DELIMITER ;

第三步：创建function nextval

DROP FUNCTION IF EXISTS nextval; 
DELIMITER $ 
CREATE FUNCTION nextval (seq_name VARCHAR(50)) 
RETURNS VARCHAR(20) 
CONTAINS SQL 
BEGIN 
   UPDATE seq SET `max` = `max` + NEXT WHERE NAME = seq_name; 
   RETURN bj(seq_name); 
END$ 
DELIMITER ; 

第四步： 插入两个seq

INSERT INTO `seq` (`name`,`max`,`length`,`next`,`rules`) VALUES ('complaint_seq_b', '0', '7', '1', 'B###max_id###' ); 


INSERT INTO `seq` (`name`,`max`,`length`,`next`,`rules`) VALUES ('complaint_seq_a', '0', '7', '1','A###max_id###'); 

第五步：测试

SELECT nextval('complaint_seq_b'); 

SELECT nextval('complaint_seq_a');