i have two tables. users and accounts.

accounts table :-

```
id  | accountName | userId
--------------------
1   |    natt     |  1
2   |    kelly    |  2
3   |    john     |  3

```

users table :-

```
id  |    username         | 
--------------------
1   |    natt@xyz.com     |
2   |    kelly@xyz.com    |
3   |    john@xyz.com     |
4   |    randy@xyz.com    |
5   |    jamie@xyz.com    |

```

expected output: -

```
userId  |
---------
4       |
5       |

```

as you can see `id` of `users` table act as `foreign key` in `accounts` table.
I want to fetch every user that does not have a `account` associated with it(4,5 in my example). i can do it via `IN or NOT IN` but thats not the fastest way. can some tell me the fastes way to do this? im using postgres.