select distinct from join - sql

Question

My Tables look like this
Table 1 Table 2
Users Options
id name id user_id option
------- --- -------- --------
1 Donald 1 1 access1
2 John 2 1 access2
3 Bruce 3 1 access3
4 Paul 4 2 access1
5 Ronald 5 2 access3
6 Steve 6 3 access1
Now, i want to select join these to find a user which has only access1
If i do something like
select t1.id,t1.name,t2.id,t2.user_id,t2.option
from table1 t1, table2 t2
where t1.id=t2.user_id
and option='access1';
This does not give me unique results, as in the example i need only user_id=3 my data has has these in hundreds
I also tried something like
select user_id from table2 where option='access1'
and user_id not in (select user_id from table2 where option<>'access1')
There have been other unsuccessful attempts too but i am stuck here

Answer 1

You can do this using a EXISTS subquery (technically, a left semijoin):
SELECT id, name
FROM table1
WHERE EXISTS(
SELECT * FROM table2
WHERE table1.id = table2.user_id
AND table2.option = 'access1'
)
If you want only users that have access1 and not any other access, add NOT EXISTS (a left anti-semi-join; there's a term to impress your colleagues!):
AND NOT EXISTS (
SELECT * FROM table2
WHERE table1.id = table2.user_id
AND table2.option <> 'access1'
)

Answer 2

bool_and makes it simple
with users (id,name) as ( values
(1,'donald'),
(2,'john'),
(3,'bruce'),
(4,'paul'),
(5,'ronald'),
(6,'steve')
), options (id,user_id,option) as ( values
(1,1,'access1'),
(2,1,'access2'),
(3,1,'access3'),
(4,2,'access1'),
(5,2,'access3'),
(6,3,'access1')
)
select u.id, u.name
from
users u
inner join
options o on o.user_id = u.id
group by 1, 2
having bool_and(o.option = 'access1')
;
id | name
----+-------
3 | bruce

Answer 3

If you want the user that has only access1, I would use aggregation:
select user_id
from table2
group by user_id
having min(option) = max(option) and min(option) = 'access1';

Answer 4

WITH users(id,name) AS ( VALUES
(1,'Donald'),
(2,'John'),
(3,'Bruce'),
(4,'Paul'),
(5,'Ronald'),
(6,'Steve')
), options(id,user_id,option) AS ( VALUES
(1,1,'access1'),
(2,1,'access2'),
(3,1,'access3'),
(4,2,'access1'),
(5,2,'access3'),
(6,3,'access1')
), user_access_count AS (
SELECT op.user_id,count(op.option) AS access_count
FROM options op
WHERE EXISTS(
SELECT 1 FROM options
WHERE option = 'access1'
)
GROUP BY op.user_id
)
SELECT u.id,u.name
FROM users u
INNER JOIN user_access_count uac ON uac.user_id = u.id
WHERE uac.access_count = 1;