Postgres FK引用复合PK

Question

考虑

CREATE TABLE foo (
    id SERIAL,
    foo_created_on ABSTIME,
    foo_deactivated_on ABSTIME,
    PRIMARY KEY (id, foo_created_on)
);

CREATE TABLE bar (
    id SERIAL,
    bar_created_on ABSTIME,
    bar_deactivated_on ABSTIME,
    foo_id REFERENCES ( .. what goes here? ..),
    PRIMARY KEY (id, bar_created_on)
);

如何在"bar"中创建引用"foo"中的PK的FK？

Answer 1

如何在"bar"中创建引用"foo"中的PK的FK？

根据您当前的结构,您不能.

必须将外键引用的目标声明为PRIMARY KEY或UNIQUE.所以要么这个

CREATE TABLE foo (
    id SERIAL PRIMARY KEY,
    foo_created_on ABSTIME,
    foo_deactivated_on ABSTIME,
    UNIQUE (id, foo_created_on)
);

或这个

CREATE TABLE foo (
    id SERIAL,
    foo_created_on ABSTIME,
    foo_deactivated_on ABSTIME,
    PRIMARY KEY (id, foo_created_on),
    UNIQUE (id)
);

将作为bar.foo_id的目标.然后吧会有一个简单的参考.

CREATE TABLE bar (
    id SERIAL,
    bar_created_on ABSTIME,
    bar_deactivated_on ABSTIME,
    foo_id REFERENCES foo (id),
    PRIMARY KEY (id, bar_created_on)
);

如果要引用最初在foo中声明的主键,则必须将该主键存储在bar中.你必须存储所有这些,而不是它的一部分.所以如果不修改foo,你可以像这样构建吧.

CREATE TABLE bar (
    id SERIAL,
    bar_created_on ABSTIME,
    bar_deactivated_on ABSTIME,
    foo_id INTEGER NOT NULL,
    foo_created_on ABSTIME NOT NULL,
    FOREIGN KEY (foo_id, foo_created_on) REFERENCES foo (id, foo_created_on),
    PRIMARY KEY (id, bar_created_on)
);

Answer 2

您必须创建单独的外键:

CREATE TABLE bar (
  id SERIAL,
  bar_created_on ABSTIME,
  bar_deactivated_on ABSTIME,
  foo_id INT,
  FOREIGN KEY (foo_id, created_on) REFERENCES foo (id, created_on),
  PRIMARY KEY (id, bar_created_on)
);