如何在PostgreSQL中插入主/外键行

Question

I'm populating a database in PostgreSQL for a Newspaper Online. Now my doubt lies on how to insert a value into a table which only attribute is both a primary and a foreign key.

In this context, the admin is the first person to ever register an account. So idAdmin = idA = 1:

CREATE TABLE AUTENTICADO (
    idA serial NOT NULL ,
    login VARCHAR(45) NOT NULL,
    password VARCHAR(45) NOT NULL,
    email VARCHAR(40) NOT NULL,
    PRIMARY KEY (idA) );

CREATE TABLE ADMIN (
    idAdmin INT  NOT NULL REFERENCES AUTENTICADO (idA),
    PRIMARY KEY (idAdmin) );

It would be logical to insert values into 'ADMIN' as I tried below, although it is obviously not possible considering 'idAdmin' is a primary key (and a foreign key).

INSERT INTO AUTENTICADO VALUES ('john','adadfsfsdfs', 'john@random.com')
INSERT INTO ADMIN VALUES (1)

Is there a way to register that the first user to create an account (idA = 1) is the admin (idAdmin = idA = 1) ?

Answer 1

although it is obviously not possible considering 'idAdmin' is a primary key (and a foreign key).

So what?

If you fix the first query to list the columns and use a returning clause to get the auto-generated value for the SERIAL ID, it just works:

INSERT INTO AUTENTICADO(login,password,email)
  VALUES ('john','adadfsfsdfs', 'john@random.com')
  returning idA;

Result:

ida 
-----
   1
(1 row)

Second query:

insert into admin values(1);
select * from admin;

Result:

idadmin 
---------
       1