postgresql 唯一约束不够唯一

Question

我正在创建表格来处理我们数据库的安全问题/选定问题/给定答案部分并收到此错误：

引用表“m_security_questions”的给定键没有唯一约束匹配

不知道如何解决这个问题？

（由于架构不会构建错误的 b/c，我无法添加 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');

Answer 1

主键明确定义了唯一约束。但是唯一的约束是在（成员，问题）上。您有两个 FOREIGN KEY 约束，分别仅引用 (member) 和 (question)。

我很确定你想要的是：

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)
  );