How to use page item value inside a trigger query in oracle?

Question

I want the following trigger to be run correctly but it rise an error which is: bad bind variable 'P23_ID'. The trigger query is:

Create or replace trigger "newTRG"
Before
Insert on "my_table"
For each row
Begin
If :new."ID" is null then
Insert into my_table (ID) values (:P23_ID);
end if;
End;

Answer 1

Use the v() syntax:

create or replace trigger "newTRG" before
   insert on "my_table"
   for each row
begin
   if :new."ID" is null then
      insert into my_table ( id ) values (v('P23_ID'));

   end if;
end;

On a side note, if this is a primary key value it is a lot easier to use identity columns (the new way) or a sequence (the old way) to populate your column. Doing this from a page item is error prone.