MySQL 数据库实现 sequence(序列)

drop table if exists sequence;   
create table sequence (       
    seq_name VARCHAR(50) NOT NULL COMMENT '序列名称',
    current_val INT NOT NULL COMMENT '当前值',
    increment_val INT NOT NULL DEFAULT 1 COMMENT '步长(跨度)',
    PRIMARY KEY (seq_name)
) ENGINE=InnoDB CHARSET=utf8mb4 COMMENT='通用队列';

INSERT INTO sequence VALUES ('seq_hello', '0', '1');

create function currval(v_seq_name VARCHAR(50))   
returns integer(11) 
begin
 declare value integer;
 set value = 0;
 select current_val into value  from sequence where seq_name = v_seq_name;
   return value;
end;

create function nextval (v_seq_name VARCHAR(50)) returns integer(11) 
begin
    update sequence set current_val = current_val + increment_val  where seq_name = v_seq_name;
    return currval(v_seq_name);
end;

select currval('seq_hello');