Postgresql how to organize delimited access - postgresql

Question

How to organize delimited access to elements correctly.
I have two main tables:
CREATE TABLE t_users (
user_id varchar PRIMARY KEY,
user_email varchar
);
CREATE TABLE t_items (
item_id varchar PRIMARY KEY,
owner_id varchar not null references t_users(user_id),
title varchar
);
I'm trying to create tables to differentiate access:
CREATE TABLE t_access_gropes (
access_group_id varchar PRIMARY KEY,
user_id varchar not null references t_users(user_id)
);
CREATE TABLE t_access_sets (
access_set_id varchar PRIMARY KEY,
item_id varchar not null references t_items(item_id),
access_group_id varchar not null references t_access_gropes(access_group_id)
);
The example data:
INSERT INTO t_users VALUES ('us123', 'us123#email.com');
INSERT INTO t_users VALUES ('us456', 'us456#email.com');
INSERT INTO t_users VALUES ('us789', 'us789#email.com');
INSERT INTO t_items VALUES ('it123', 'us123', 'title1');
INSERT INTO t_items VALUES ('it456', 'us456', 'title2');
INSERT INTO t_items VALUES ('it678', 'us789', 'title3');
INSERT INTO t_items VALUES ('it323', 'us123', 'title4');
INSERT INTO t_items VALUES ('it764', 'us456', 'title5');
INSERT INTO t_items VALUES ('it826', 'us789', 'title6');
INSERT INTO t_items VALUES ('it568', 'us123', 'title7');
INSERT INTO t_items VALUES ('it038', 'us456', 'title8');
INSERT INTO t_items VALUES ('it728', 'us789', 'title9');
INSERT INTO t_access_gropes VALUES ('ag123', 'us123');
INSERT INTO t_access_gropes VALUES ('ag456', 'us456');
INSERT INTO t_access_gropes VALUES ('ag789', 'us789');
INSERT INTO t_access_sets VALUES ('as123', 'it123', 'ag123');
INSERT INTO t_access_sets VALUES ('as456', 'it456', 'ag123');
In the end, I want to get a differentiation of access rights.
Access kind:
Public
Private
For friends.
My query:
select *
from t_items
inner join t_users on t_items.owner_id = t_users.user_id
inner join t_access_gropes on t_users.user_id = t_access_gropes.user_id
inner join t_access_sets on t_items.item_id = t_access_sets.item_id
where t_access_gropes.user_id = 'us123';
works but returns only one value.
Thank you.

Answer 1

I think you want LEFT OUTER JOIN on t_access_sets
SQL Fiddle
Query 1:
SELECT i.*,
u.user_email,
g.access_group_id,
s.access_set_id
FROM t_items i
join t_users u
ON i.owner_id = u.user_id
join t_access_gropes g
ON u.user_id = g.user_id
left outer join t_access_sets s
ON i.item_id = s.item_id
WHERE u.user_id = 'us123'
Results:
| item_id | owner_id | title | user_email | access_group_id | access_set_id |
|---------|----------|--------|-----------------|-----------------|---------------|
| it123 | us123 | title1 | us123#email.com | ag123 | as123 |
| it323 | us123 | title4 | us123#email.com | ag123 | (null) |
| it568 | us123 | title7 | us123#email.com | ag123 | (null) |