Insert data into strongly normalized DB and maintain the integrity (Postgres) - postgresql

Question

I'm trying to develop a simple database for the phonebook. This is what I wrote:
CREATE TABLE phone
(
phone_id SERIAL PRIMARY KEY,
phone CHAR(15),
sub_id INT, -- subscriber id --
cat_id INT -- category id --
);
CREATE TABLE category
(
cat_id SERIAL PRIMARY KEY, -- category id --
cat_name CHAR(15) -- category name --
);
CREATE TABLE subscriber
(
sub_id SERIAL PRIMARY KEY,
name CHAR(20),
fname CHAR(20), -- first name --
lname CHAR(20), -- last name --
);
CREATE TABLE address
(
addr_id SERIAL PRIMARY KEY,
country CHAR(20),
city CHAR(20),
street CHAR(20),
house_num INT,
apartment_num INT
);
-- many-to-many relation --
CREATE TABLE sub_link
(
sub_id INT REFERENCES subscriber(sub_id),
addr_id INT
);
I created a link table for many-to-many relation because few people can live at the same address and one person can live in different locations at different times.
But I cannot figure out how to add data in strongly normalized DB like this and maintain the integrity of the data.
The first improvement was that I added inique key on address table bacause this table should not contain duplicated data:
CREATE TABLE address
(
addr_id SERIAL PRIMARY KEY,
country CHAR(20),
city CHAR(20),
street CHAR(20),
house_num INT,
apartment_num INT,
UNIQUE (country, city, street, house_num, apartment_num)
);
Now the problem is how to add a new record about some person into DB. I think I should use the next order of actions:
Insert a record into subscriber table, because sub_link and phone tables must use id of a new subscriber.
Insert a record into address table because addr_id must exist before adding record into sub_link.
Link last records from subscriber and address in sub_link table. But at this step I have a new problem: how can I get sub_id and addr_id from steps 1) and 2) in PostgreSQL effectively?
Then I need to insert a record into the phone table. As at 3) step I dont know how to get sub_id from previous queries effectively.
I read about WITH block in the Postgres but I cannot figure out how to use it in my case.
UPDATE
I've done like ASL suggested:
-- First record --
WITH t0 AS (
WITH t1 AS (
INSERT INTO subscriber
VALUES(DEFAULT, 'Twilight Sparkle', NULL, NULL)
RETURNING sub_id
),
t2 AS (
INSERT INTO address
VALUES(DEFAULT, 'Equestria', 'Ponyville', NULL, NULL, NULL)
RETURNING addr_id
)
INSERT INTO sub_link
VALUES((SELECT sub_id FROM t1), (SELECT addr_id FROM t2))
)
INSERT INTO phone
VALUES (DEFAULT, '000000', (SELECT sub_id FROM t1), 1);
But I have an error: WITH clause containing a data-modifying statement must be at the top level
LINE 2: WITH t1 AS (INSERT INTO subscriber VALUES(DEFAULT,

Answer 1

You can do it all in one query using a WITH block with a RETURNING clause. See PostgreSQL docs on INSERT. For example:
WITH t1 AS (INSERT INTO subscriber VALUES ... RETURNING sub_id),
t2 AS (INSERT INTO address VALUES ... RETURNING addr_id)
INSERT INTO sub_link VALUES ((SELECT sub_id FROM t1), (SELECT addr_id FROM t2))
Note that this simple form will only work when inserting a single row into each table.
This is somewhat off the topic of your question, but I suggest you also consider making sub_id and cat_id columns in the phone table foreign keys (use REFERENCES).

Answer 2

You got the idea. Insert data from topmost tables so that you have their IDs before inserting references to them.
In PostgreSQL you can use INSERT/UPDATE ... RETURNING id construct. If you are not using some ORM which do it automatically, this may be useful.
The only thing here is that in step 2 you probably want to check if the address already exists before inserting:
SELECT addr_id FROM address WHERE country = ? AND city = ? ...