ERROR: No unique constraint matching when having FK - sql

Question

I have three tables that are linked together
My script:
-- Ticket --
CREATE TABLE public.ticket (
id bigint NOT NULL,
libelle character varying(255) NOT NULL,
description character varying(255) NOT NULL,
status character varying(255) NOT NULL,
date_creation timestamp NOT NULL,
date_modification timestamp NOT NULL,
user_createur_id bigint,
referent_realisateur_id bigint,
CONSTRAINT pk_ticket PRIMARY KEY (id)
);
-- Ticket_Avance TABLE --
CREATE TABLE public.ticket_avance (
id bigint NOT NULL,
date_livraison_souhaite timestamp NOT NULL,
date_engagement_livraison timestamp NOT NULL,
referent_demandeur_id bigint
);
ALTER TABLE public.ticket_avance ADD CONSTRAINT "fk_ticket_ticketAvance" FOREIGN KEY (id)
REFERENCES public.ticket (id) MATCH SIMPLE
ON DELETE NO ACTION ON UPDATE NO ACTION;
-- Demande_Travaux TABLE --
DROP TABLE IF EXISTS public.demande_travaux CASCADE;
CREATE TABLE public.demande_travaux (
id bigint NOT NULL,
contrat_id bigint
);
ALTER TABLE public.demande_travaux ADD CONSTRAINT "fk_ticketAvance_DDT" FOREIGN KEY (id)
REFERENCES public.ticket_avance (id) MATCH FULL
ON DELETE NO ACTION ON UPDATE NO ACTION;
I have this error on the demand_travaux creation
SQL Error [42830]: ERROR: there is no unique constraint matching given keys for referenced table "ticket_avance"
ERROR: there is no unique constraint matching given keys for referenced table "ticket_avance"
ERROR: there is no unique constraint matching given keys for referenced table "ticket_avance"

Answer 1

You have forgotten to declare column ID in table ticket_avance as primary key.
Please use the following SQL:
-- Ticket_Avance TABLE --
CREATE TABLE public.ticket_avance (
id bigint NOT NULL,
date_livraison_souhaite timestamp NOT NULL,
date_engagement_livraison timestamp NOT NULL,
referent_demandeur_id bigint,
CONSTRAINT pk_avance PRIMARY KEY (id) --- add this
);

Answer 2

you need add constraint in Ticket_Avance table because you provide reference this id to demande_travaux
-- Ticket_Avance TABLE --
CREATE TABLE ticket_avance (
id bigint NOT NULL,
date_livraison_souhaite timestamp NOT NULL,
date_engagement_livraison timestamp NOT NULL,
referent_demandeur_id bigint,
CONSTRAINT pk_ticket_avance PRIMARY KEY (id) //constraint that you need
);
ALTER TABLE demande_travaux ADD CONSTRAINT "fk_ticketAvance_DDT" FOREIGN KEY (id)
REFERENCES ticket_avance (id) MATCH FULL
ON DELETE NO ACTION ON UPDATE NO ACTION;
here is the demo link of your full query

Answer 3

A foreign key constraint has to target a primary key or unique constraint. The database has to be able to identify a single row in the "parent" table.
You could add primary key constraints:
ALTER TABLE public.ticket_avance ADD PRIMARY KEY (id);
In addition, you should have an index on the column on which the foreign key is defined, particularly if you plan to delete parent rows. With the primary key above, you have such an index on id, but you also should have one on demande_travaux.
The simplest way is to define id as primary key there too:
ALTER TABLE public.demande_travaux ADD PRIMARY KEY (id);