il vincolo univoco di postgresql non è abbastanza unico - postgresql, vincoli, unico

Sto creando tabelle per gestire la domanda di sicurezza / domanda selezionata / sezione risposta data del nostro database e ottenere questo errore:

non esiste un vincolo univoco con chiavi date per la tabella di riferimento "m_security_questions"

Non sei sicuro di come lo risolvo?

(Dato che lo schema ha vinto "t build b / c of error, I couldn" t aggiungere SQL Fiddle)

CREATE TABLE security_question --defines questions
(
id SERIAL PRIMARY KEY NOT NULL,
question character varying(1024) NOT NULL,
is_custom boolean DEFAULT FALSE NOT NULL
);

INSERT INTO security_question
(question,is_custom)
VALUES
("do you know the answer?",FALSE),
("Write your own question",TRUE);

CREATE TABLE m_security_questions
( --defines question a member chooses & allows free form question
-- id SERIAL NOT NULL,
-- I know adding id like this and making keeping same pk solves it
-- but isn"t storing the extra sequence not needed?
member integer --REFERENCES member(m_no)
-- commented out reference for so only
NOT NULL,
question integer REFERENCES security_question(id) NOT NULL,
m_note text,
PRIMARY KEY(member,question)
);

-- here I add unique constraint but doesn"t the primary already mean I have a unique index?
ALTER TABLE m_security_questions ADD CONSTRAINT m_security_questions_unique_member_question UNIQUE (member,question);

INSERT INTO m_security_questions
(member,question,m_note)
VALUES
(2,1,NULL),
(2,2,"How many marbles in this jar?");


CREATE TABLE m_security_answer --defines members given answer
( -- I want member & question here to line up w/ same from m_security_questions
member integer REFERENCES m_security_questions(member),
question integer REFERENCES m_security_questions(question) NOT NULL,
answer character varying(255) NOT NULL,
PRIMARY KEY (member,question)
);
-- here is where I get the error:
-- there is no unique constraint matching given keys for referenced table "m_security_questions"

INSERT INTO m_security_answer
(member,question,answer)
VALUES
(2,1,"yes"),
(2,2,"431");

risposte:

La chiave primaria definisce definitivamente un unicovincolo. Ma il vincolo univoco è attivo (membro, domanda). Hai due vincoli FOREIGN KEY che fanno riferimento solo a (membro) e (domanda) separatamente.

Sono abbastanza sicuro di quello che vuoi è:

CREATE TABLE m_security_answer --defines members given answer
(
member integer,
question integer NOT NULL,
answer character varying(255) NOT NULL,
PRIMARY KEY (member,question),
FOREIGN KEY (member, question) REFERENCES m_security_questions(member, question)
);