当前位置：文江博客话题详情

在 MySQL/InnoDB 中模拟自动增量

发布于 2024-09-10 08:14:38 字数 145 浏览 4 评论 0原文

假设我要

条件

使用 MySQL/InnoDB 模拟 MySQL/InnoDB
中的自动增量ID 字段没有唯一索引，也不是 PK

是否可以仅使用程序逻辑来模拟，而不使用表级锁。谢谢。

原文

分享到QQ

分享到微博

如果你对这篇内容有疑问，欢迎到本站社区发帖提问参与讨论，获取更多帮助，或者扫码二维码加入 Web 技术交流群。

发布评论

需要登录才能够评论，你可以免费注册一个本站的账号。

逆光下的微笑 2024-09-17 08:14:39

使用序列表和触发器 - 像这样：

drop table if exists users_seq;

create table users_seq
(
next_seq_id int unsigned not null default 0
)engine = innodb;

drop table if exists users;

create table users
(
user_id int unsigned not null primary key,
username varchar(32) not null
)engine = innodb;

insert into users_seq values (0);

delimiter #

create trigger users_before_ins_trig before insert on users
for each row
begin

declare id int unsigned default 0;

  select next_seq_id + 1 into id from users_seq;

  set new.user_id = id;

  update users_seq set next_seq_id = id;

end#

delimiter ;

insert into users (username) values ('f00'),('bar'),('bish'),('bash'),('bosh');

select * from users;
select * from users_seq;

insert into users (username) values ('newbie');

select * from users;
select * from users_seq;

Use a sequence table and a trigger - something like this:

drop table if exists users_seq;

create table users_seq
(
next_seq_id int unsigned not null default 0
)engine = innodb;

drop table if exists users;

create table users
(
user_id int unsigned not null primary key,
username varchar(32) not null
)engine = innodb;

insert into users_seq values (0);

delimiter #

create trigger users_before_ins_trig before insert on users
for each row
begin

declare id int unsigned default 0;

  select next_seq_id + 1 into id from users_seq;

  set new.user_id = id;

  update users_seq set next_seq_id = id;

end#

delimiter ;

insert into users (username) values ('f00'),('bar'),('bish'),('bash'),('bosh');

select * from users;
select * from users_seq;

insert into users (username) values ('newbie');

select * from users;
select * from users_seq;

回复收藏 0 原文

酒儿 2024-09-17 08:14:39

CREATE TABLE sequence (id INTEGER); -- possibbly add a name;
INSERT INTO sequence VALUES (1); -- starting value

SET AUTOCOMMIT=0;
START TRANSACTION;
UPDATE sequence SET id = LAST_INSERT_ID(id+1);
INSERT INTO actualtable (non_autoincrementing_key) VALUES (LAST_INSERT_ID());
COMMIT;

SELECT LAST_INSERT_ID(); 甚至是一个会话安全值，用于检查您获得的 ID。确保您的表支持事务，或者序列中的漏洞没有问题。

CREATE TABLE sequence (id INTEGER); -- possibbly add a name;
INSERT INTO sequence VALUES (1); -- starting value

SET AUTOCOMMIT=0;
START TRANSACTION;
UPDATE sequence SET id = LAST_INSERT_ID(id+1);
INSERT INTO actualtable (non_autoincrementing_key) VALUES (LAST_INSERT_ID());
COMMIT;

SELECT LAST_INSERT_ID(); Is even a session-safe value to check which ID you got. Be sure your table support transactions, or that holes in a sequence are no problem.

回复收藏 0 原文