mysql实现自增序列的示例代码

1.创建sequence表

create table `sequence` (
 `name` varchar(50) collate utf8_bin not null comment '序列的名字',
 `current_value` int(11) not null comment '序列的当前值',
 `increment` int(11) not null default '1' comment '序列的自增值',
 primary key (`name`)
) engine=innodb default charset=utf8 collate=utf8_bin;

2.创建–取当前值的函数

drop function if exists currval; 
delimiter $ 
create function currval (seq_name varchar(50)) 
   returns integer
   language sql 
   deterministic 
   contains sql 
   sql security definer 
   comment ''
begin
   declare value integer; 
   set value = 0; 
   select current_value into value 
     from sequence
     where name = seq_name; 
   return value; 
end
$ 
delimiter ; 

3.创建–取下一个值的函数

drop function if exists nextval; 
delimiter $ 
create function nextval (seq_name varchar(50)) 
   returns integer 
   language sql 
   deterministic 
   contains sql 
   sql security definer 
   comment '' 
begin 
   update sequence 
     set current_value = current_value + increment 
     where name = seq_name; 
   return currval(seq_name); 
end 
$ 
delimiter ; 

4.创建–更新当前值的函数

drop function if exists setval; 
delimiter $ 
create function setval (seq_name varchar(50), value integer) 
   returns integer 
   language sql 
   deterministic 
   contains sql 
   sql security definer 
   comment '' 
begin 
   update sequence 
     set current_value = value 
     where name = seq_name; 
   return currval(seq_name); 
end 
$ 
delimiter ; 

5.测试添加实例 执行sql

insert into sequence values ('testseq', 0, 1);-- 添加一个sequence名称和初始值，以及自增幅度
 
select setval('testseq', 10);-- 设置指定sequence的初始值
 
select currval('testseq');-- 查询指定sequence的当前值
 
select nextval('testseq');-- 查询指定sequence的下一个值

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