是一种数据库项,可以生成整数序列。
create sequence s_test start with 10 increment by 5 minvalue 10 maxvalue 20 cycle cache 2 order;
select sequence_name, min_value, max_value, increment_by, cycle_flag,order_flag, cache_size, last_number from user_sequences order by sequence_name;
select s_test.nextval from dual; NEXTVAL -------- 1 select s_test.currval from dual; CURRVAL -------- 1
create table order ( id integer constraint order_pk primary key, status varchar2(10); last_modified DATE default sysdate ); create sequence s_order nocache; insert into order(id, status, last_modified) values(s_order.nextval, 'placed', '2017-11-09');
create sequence s_default_value_for_column; create table test_with_sequence( id integer constraint test_with_pk primary key, sequence_value integer default s_default_value_for_column.nextval )
oracle database 12c的新功能
create table test_with_identity( id integer constraint test_with__identity_pk primary key, identity_value integer generated by default as identity( start with 5 increment by 2 ) )
alter sequence s_test increment by 2;
drop sequence s_test;
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