Text array of integers for joining tables in Postgres - postgresql

Question

I have two tables
Entity
House
In house table, there is a column entity_id of type text.
And entity_id will store multiple house ids.
So it will look like
entity_id (text)
------------------
[1,2]
[3,6]
Now I have to join this entity table with house table.
How will I achieve this.
I know this may not be a good design. Though now this my responsibility to do this.

Answer 1

This should work:
CREATE TABLE entity(
id integer,
entity_id integer[],
details text
);
CREATE TABLE houses(
id integer,
house_name text
);
INSERT INTO entity(id, entity_id, details)
VALUES
(1, '{1,3}', 'Left side houses'),
(2, '{2,4}', 'Right side houses');
INSERT INTO houses(id, house_name)
VALUES
(1, 'Left 1'),
(2, 'Right 1'),
(3, 'Left 2'),
(4, 'Right 2');
----------------------------------------------
SELECT h.id as house_id, h.house_name, e.details
FROM houses h
LEFT JOIN entity e
ON h.id = ANY(e.entity_id);
| house_id | house_name | details |
| -------- | ---------- | ----------------- |
| 1 | Left 1 | Left side houses |
| 2 | Right 1 | Right side houses |
| 3 | Left 2 | Left side houses |
| 4 | Right 2 | Right side houses |

Answer 2

As Laurenz says in comment: it seems to be an error of modelisation here.
So I will not directly answer to the question but I will give a most correct structure :
CREATE TABLE entity (id int primary key);
CREATE TABLE house (id int primary key);
CREATE TABLE entity_house (id bigserial, identity int references entity(id), idhouse int references house(id));
INSERT INTO entity VALUES (1), (2);
INSERT INTO house VALUES (3), (56);
INSERT INTO entity_house (identity, idhouse) VALUES (1,56), (2,56);
SELECT e.*, h.*
FROM entity_house eh
INNER JOIN entity e ON eh.identity = e.id
INNER JOIN house h ON eh.idhouse = h.id;