The table is as follows.
create table ventas(
id_venta number(5) primary key,
id_articulo number(5) references articulos,
id_empleado number(6) references empleado,
id_cliente number(5) references cliente,
cantidad number(10) not null,
precio number(8) not null,
total number(8) not null,
fecha_venta date
);
To solve this, you just need a trigger and using a sequence like the one presented here.
create sequence Auidventa
start with 1
increment by 1 -- aqui lo hago es que determino apartir de que nuevo voy
-- a iniciar y cuando va incrementar
order;
-- Creacion de trigger
create or replace trigger autoidventa
before insert on ventas
for each row
begin
select Auidventa.nextval into :new.id_venta from dual;
end;
/
Now only that it gives to realize the common insertion in the table advantages but eye does not specify the field id_venta, that is to say it does not insert there since that the autoincrementable field.