Oracle取顺序流水号(解决了并发的问题)

--取顺序流水号(使用了自治事务及悲观锁)
流水号记录表: Tcount表(X int,item varchar(20)) 主键:x+item做为联合主键

procedure getX(p_item varchar2,cu out number)
is
begin
cu:=0;
autonomous_insert(p_item);

select x+1 into cu from tcount where item=p_item for update;
update tcount set x=x+1 where item=p_item;
--commit;
end;


procedure autonomous_insert(p_item varchar2)
is
--使用自治事务
pragma autonomous_transaction;
begin
insert into tcount
select 0,p_item from dual where not exists(select 1 from tcount t where t.item=p_item) ;

commit;
exception when others then
rollback;
end;