Select rows with no match in join table with where condition - ruby-on-rails

Question

In a Rails app with Postgres I have a users, jobs and followers join table. I want to select jobs that are not followed by a specific user. But also jobs with no rows in the join table.
Tables:
users:
id: bigint (pk)
jobs:
id: bigint (pk)
followings:
id: bigint (pk)
job_id: bigint (fk)
user_id: bigint (fk)
Data:
sandbox_development=# SELECT id FROM jobs;
id
----
1
2
3
(3 rows)
sandbox_development=# SELECT id FROM users;
id
----
1
2
sandbox_development=#
SELECT id, user_id, job_id FROM followings;
id | user_id | job_id
----+---------+--------
1 | 1 | 1
2 | 2 | 2
(2 rows)
Expected result
# jobs
id
----
2
3
(2 rows)
Can I create a join query that is the equivalent of this?
sandbox_development=#
SELECT j.id FROM jobs j
WHERE NOT EXISTS(
SELECT 1 FROM followings f
WHERE f.user_id = 1 AND f.job_id = j.id
);
id
----
2
3
(2 rows)
Which does the job but is a PITA to create with ActiveRecord.
So far I have:
Job.joins(:followings).where(followings: { user_id: 1 })
SELECT "jobs".* FROM "jobs"
INNER JOIN "followings"
ON "followings"."job_id" = "jobs"."id"
WHERE "followings"."user_id" != 1
But since its an inner join it does not include jobs with no followers (job id 3). I have also tried various attempts at outer joins that either give all the rows or no rows.

Answer 1

In Rails 5, You can use #left_outer_joins with where not to achieve the result. Left joins doesn't return null rows. So, We need to add nil conditions to fetch the rows.
Rails 5 Query:
Job.left_outer_joins(:followings).where.not(followings: {user_id: 1}).or(Job.left_outer_joins(:followings).where(followings: {user_id: nil}))
Alternate Query:
Job.left_outer_joins(:followings).where("followings.user_id != 1 OR followings.user_id is NULL")
Postgres Query:
SELECT "jobs".* FROM "jobs" LEFT OUTER JOIN "followings" ON "followings"."job_id" = "jobs"."id" WHERE "followings"."user_id" != 1 OR followings.user_id is NULL;

Answer 2

I'm not sure I understand, but this has the output you want and use outer join:
SELECT j.*
FROM jobs j LEFT JOIN followings f ON f.job_id = j.id
LEFT JOIN users u ON u.id = f.user_id AND u.id = 1
WHERE u.id IS NULL;