MySQL 新增序列三步曲
2021/12/29 19:08:17
本文主要是介绍MySQL 新增序列三步曲,对大家解决编程问题具有一定的参考价值,需要的程序猿们随着小编来一起学习吧!
1、创建一个统一管理序列的表sequences
drop table if exists sequences; create table sequences ( SEQUENCE_NAME varchar(80) not null comment '自增序列名称' primary key, INCREMENT_BY int not null comment '步长', CURRENT_VALUE bigint not null comment '当前值', MIN_VALUE bigint null comment '最小值', MAX_VALUE bigint null comment '最大值', COMMENTS varchar(200) null comment '序列描述', CYCLE varchar(10) null comment '当值为CYCLE时,代表循环' );
2、创建一个自增序列函数
drop function if exists nextval; create function nextval(a_seq_name varchar(55)) returns bigint BEGIN DECLARE seq_val BIGINT; DECLARE min_val BIGINT; DECLARE max_val BIGINT; DECLARE cycle_val VARCHAR(10); SET seq_val = -1; IF EXISTS(SELECT 1 FROM sequences holdlock WHERE SEQUENCE_NAME = a_seq_name) THEN SELECT CURRENT_VALUE + INCREMENT_BY, MIN_VALUE, MAX_VALUE, CYCLE INTO seq_val, min_val, max_val, cycle_val FROM sequences WHERE SEQUENCE_NAME = a_seq_name FOR UPDATE; IF seq_val > max_val THEN IF cycle_val = 'CYCLE' THEN SET seq_val = min_val; ELSE SIGNAL SQLSTATE '42000' SET MESSAGE_TEXT ='error:1000,sequence beyond the max value '; END IF; END IF; UPDATE sequences SET CURRENT_VALUE = seq_val WHERE SEQUENCE_NAME = a_seq_name; ELSE SIGNAL SQLSTATE '42000' SET MESSAGE_TEXT ='error:1001,Query was empty,sequence name not found '; END IF; RETURN seq_val; END;
3、插入数据
insert into sequences(sequence_name, increment_by, current_value, min_value, max_value, comments, cycle) value ('PHONE_NBR_SEQ', 1, 20221001, 20221001, 9999999999, '手机号码序列', null);
4、查询序列
select nextval('PHONE_NBR_SEQ') from dual; //可省略
完
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