Sequences 的作用

create sequence seq2
start with 0 --起始值
increment by 1 --步长
maxvalue 4999 --最大值
minvalue 0 --最小值
cycle --循环
cache 4 --缓存4个数

create table testa(
ins number(4) primary key,
nm varchar2(20));

-- Created on 2007-10-17 by YCZ
declare
-- Local variables here
i integer;
begin
-- Test statements here
for i in 1..5000 loop
begin
insert into testa(ins,nm) values (seq2.nextval,'N');
commit;
end;
end loop;
end;

select * from testa