Oracle defines self incrementing primary keys through triggers and sequences, and sets a scheduled task to insert a piece of data into the target table every second

create table classinfo(
       classid number(2) primary key,
       classname varchar(10) not null       
);
       
-- Create sequence 
create sequence CLASSINFO_SEQ
minvalue 1
maxvalue 9999999999999999999999999999
start with 1
increment by 1
nocache;

       
CREATE OR REPLACE TRIGGER 
CLASSINFO_TRIGGER
before insert on classinfo
for each row
declare
begin
select CLASSINFO_SEQ.NEXTVAL into :NEW.classid from DUAL;
end ;

insert into classinfo values(null,'aaa');
insert into classinfo values(null,'aaa');
insert into classinfo values(null,'aaa');
insert into classinfo values(null,'aaa');

select * from classinfo

create or replace procedure CLASSINFO_PRO is
begin
  insert into classinfo values(null,'aaa');
end CLASSINFO_PRO;


declare
  job number;
BEGIN
  DBMS_JOB.SUBMIT(  
        JOB => job,  /* Automatic generation JOB_ID*/  
        WHAT => 'CLASSINFO_PRO;',  /* The name of the stored procedure to execute or SQL sentence */  
        NEXT_DATE => sysdate+1/(24*60),  /* First execution time next minute */  
        INTERVAL => 'sysdate+1/(24*60*60)' /* every other 1 Once per second */
      );  
  commit;
end;


select * from user_jobs;