postgresql key contraint fault - postgresql

Question

I try to create code for postgresql
CREATE TABLE kaart (
kaartid integer NOT NULL,
naam character varying,
saldo real,
kaarthouderid integer
);
CREATE TABLE kaart_product (
kaartkaartid integer,
productid2 integer
);
CREATE TABLE kaarthouder (
id integer NOT NULL,
naam character varying(255),
naw character varying(255),
geslacht "char"
);
CREATE TABLE product (
naam character varying,
id integer NOT NULL
);
ALTER TABLE ONLY kaart
ADD CONSTRAINT kaart_pkey PRIMARY KEY (kaartid);
ALTER TABLE ONLY kaarthouder
ADD CONSTRAINT kaarthouder_pkey PRIMARY KEY (id);
ALTER TABLE ONLY product
ADD CONSTRAINT product_pkey PRIMARY KEY (id);
ALTER TABLE ONLY kaart
ADD CONSTRAINT kaartco FOREIGN KEY (kaartid) REFERENCES kaarthouder(id) ON UPDATE CASCADE ON DELETE CASCADE;
ALTER TABLE ONLY kaart_product
ADD CONSTRAINT kaartkaartidco FOREIGN KEY (kaartkaartid) REFERENCES kaart(kaartid) ON UPDATE CASCADE ON DELETE CASCADE;
ALTER TABLE ONLY kaart_product
ADD CONSTRAINT productidco FOREIGN KEY (kaartkaartid) REFERENCES product(id) ON UPDATE CASCADE ON DELETE CASCADE;
INSERT INTO kaart VALUES (1, 'Sander',50.00 ,1);
INSERT INTO kaart_product VALUES (1,1);
INSERT INTO kaarthouder VALUES (1, 'Sander','test,testing','man');
INSERT INTO product VALUES ('studentenproduct',1);
But whenever i try to run it it gives me this error:
23503: insert or update on table "kaart" violates foreign key constraint "kaartco"
But i really dont know why this happens since it is the same to the other foreign keys that are below it
So can someone help me fix this?

Answer 1

You try to link to a product and a kaart that doesn't exist yet.
Move:
INSERT INTO kaart_product VALUES (1,1);
Two lines down under:
INSERT INTO product VALUES ('studentenproduct',1);
That should do the job for you.
Try to search google for forgein key contstraints and how they work.