Duplicate rows

[Bob Pawley <rjpawley@xxxxxxx>]

I have the following _expression_ working in that the process.fluid_id is transfereed to pipe.fluid_id when the column - process.contain has a value of 'ip'.

There is no transfer when the contain column holds other values. Success - so far.

 

How do I keep the table pipe from being populated with duplicate rows? Among other reasons not to have duplicate rows,  I want to make pipe.fluid_id a primary key.

 

Bob

 

CREATE TABLE pipe (  fluid_id int4 NOT NULL);
CREATE TABLE process( fluid_id int4 NOT NULL, process varchar, contain varchar) ;

create or replace function base() returns trigger as $$
 DECLARE
 myrow RECORD;
 BEGIN
 
    for myrow in select * from process where contain = 'ip' loop
         insert into pipe(fluid_id) values (myrow.fluid_id);
         if not found then
            do nothing ;
 

        end if;
    end loop;
    return NULL;
 END;
 $$ language plpgsql;

 

 create trigger trig1 after insert on process
 for each row execute procedure base();

 

 insert into process (fluid_id, process, contain)
 values ('1', 'water3', 'ip');