MAXVALUE 10000 CYCLE CACHE 20; 修改很有用,最典型的情况是“需要把sequence 的current value改大一点,避免程序报错!”。你就可以看看current value是多少,然后修改increment by 足够大的值,然后执行.nextval,最后别忘了再将increnent by改成原来的值,还要注意做这些工作的前提是当前没有人用此sequence。 使用sequ...
其中last即为 Sequence 在 Session 中的当前值,即 current_value,cached为 Sequence 在 Session 中的缓存值,即 cached_value,increment记录了步长,有了这三个值即可满足 Sequence 缓存的基本条件。 对于Sequence Session Cache 与页面值之间的关系,如下图所示: 类似于log_cnt,cache_cnt即为用户在定义 Sequence 时,...
-- Accessing current sequence value without incrementing SELECT EXAMPLE_SEQUENCE.currval FROM dual; 但是,当您需要一个接一个地检索序列中的一个值时,请使用 NEXTVAL: -- Accessing the next sequence value SELECT EXAMPLE_SEQUENCE.nextval FROM dual; 正如您所看到的,每次执行此查询时,Oracle 都会从我们之前...
Oracle中有Sequence序列生成器用于生成表的主键值,官方定义:Sequencesare database objects from which multiple users can generate unique integers. The sequence generator generates sequential numbers, which can help to generate unique primary keys automatically, and to coordinate keys across multiple rows or ...
更多信息,参考Oracle 联机文档: CACHE CACHE(CEIL (MAXVALUE - MINVALUE)) / ABS (INCREMENT) CACHENote: CACHENOCACHE NOCACHECACHENOCACHEORDERto guarantee that sequence numbers are generated in order of request. This clause is useful if you are using the sequence numbers as timestamps. Guaranteeing...
By finding out the current value of the sequence and altering the increment by to be negative that number and selecting the sequence once -- the sequence can be reset to 0. If any session attempts to use the sequence while this is happening an ORA-08004 error will be generated.CREATE SEQ...
Sequence对象对于Oracle用户来说是最熟悉不过的数据库对象了,现在在SQL Server中终于也看到了类似的对象,只是在使用的语法上有一点点不一样。创建语法也是CREATE SEQUENCE,使用的时候需要使用NEXT VALUE FOR来取下一个值: 1.用法 createsequence sq_1 asbigint ...
The syntax to create a sequence in Oracle is: CREATE SEQUENCE sequence_name MINVALUE value MAXVALUE value START WITH value INCREMENT BY value CACHE value; sequence_name The name of the sequence that you wish to create. Example Let's look at an example of how to create a sequence in Oracl...
CREATE TABLE schema.sequence_name ( `currval` bigint(21) NOT NULL COMMENT 'current value', `nextval` bigint(21) NOT NULL COMMENT 'next value', `minvalue` bigint(21) NOT NULL COMMENT 'min value', `maxvalue` bigint(21) NOT NULL COMMENT 'max value', `start` bigint(21) NOT NULL ...
Oracle Sequence Cache 参数说明 一. 理论知识 先看一个创建Sequence的语句: SQL> create sequence seq_tmp 2 increment by 1 3 start with 1 4 nomaxvalue 5 nocycle 6 ; 序列已创建。 相关参数说明: INCREMENT BY 1 -- 每次加几个 START WITH 1 -- 从1开始计数...