注意参数类型，不能是number(6)
create or replace procedure pur_num_dec_pro(purid in number,nnn in number)
is
begin
update t_purchase p set p.pur_num = p.pur_num - nnn where p.pur_id = purid;
end pur_num_dec_pro;
declare
purid number:=100000;
nnn number:=2;
begin
pur_num_dec_pro(purid,nnn);
end;
