Let's assume I have a table magazine:

CREATE TABLE magazine
(
  magazine_id integer NOT NULL DEFAULT nextval(('public.magazine_magazine_id_seq'::text)::regclass),
  longname character varying(1000),
  shortname character varying(200),
  issn character varying(9),
  CONSTRAINT pk_magazine PRIMARY KEY (magazine_id)
);

And another table issue:

CREATE TABLE issue
(
  issue_id integer NOT NULL DEFAULT nextval(('public.issue_issue_id_seq'::text)::regclass),
  number integer,
  year integer,
  volume integer,
  fk_magazine_id integer,
  CONSTRAINT pk_issue PRIMARY KEY (issue_id),
  CONSTRAINT fk_magazine_id FOREIGN KEY (fk_magazine_id)
      REFERENCES magazine (magazine_id) MATCH SIMPLE
      ON UPDATE NO ACTION ON DELETE NO ACTION
);

Current INSERTS:

INSERT INTO magazine (longname,shotname,issn)
VALUES ('a long name','ee','1111-2222');

INSERT INTO issue (fk_magazine_id,number,year,volume)
VALUES (currval('magazine_magazine_id_seq'),'8','1982','6');

Now a row should only be inserted into 'magazine', if it does not already exist. However if it exists, the table 'issue' needs to get the 'magazine_id' of the row that already exists in order to establish the reference.

How can i do this?

Thx in advance!