postgresql中的双外键

Question

我试图使用双主键作为外键.

Create table AAA (
   AAA_id int primary key
);

create table BBB (
   AAA_id int,
   BBB_name character varying(20),
   primary key (AAA_id, BBB_name)
);

create table CCC (
    AAA_id,
    BBB_name,
    DDD_id,

    ... ???
);

表AAA是一个对象

表BBB与AAA有多对一,并且拥有AAA的别名

我正在尝试创建一个数据透视表,CCC在DDD和BBB之间保持多对一.

我想我想要类似的东西

create table CCC (
    AAA_id,
    BBB_name,
    DDD_id,
    foreign key (AAA_id, BBB_name) references BBB(AAA_id, BBB_name) on update cascade
);

其中AAA_id和BBB_name都是外键,但它们也始终引用BBB中的同一行.

但当然这是无效的.在postgreSQL中产生这种行为的最佳方法是什么？

Answer 1

Create temp table AAA (
   AAA_id int primary key
);

create temp table BBB (
   AAA_id int not null references AAA (AAA_id),
   BBB_name character varying(20) not null,
   primary key (AAA_id, BBB_name)
);

create temp table CCC (
    AAA_id int not null,
    BBB_name character varying(20) not null,
    DDD_id integer not null,
    -- Guessing at the primary key.
    primary key (AAA_id, BBB_name, DDD_id),
    foreign key (AAA_id, BBB_name) references BBB (AAA_id, BBB_name) 
        on update cascade
);

由于{AAA_id,BBB_name}唯一地标识BBB中的行,因此CCC中的外键{AAA_id,BBB_name}也将引用BBB中的一个唯一行.