postgresql key contraint fault

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.