I'm trying to create a query but I don't know how. 

I have three tables: `chat`, `chat_user` and `user`

Something like:

```
 ---------      ------------------------       ------------------
|  chat   |    |        chat_user       |     |       user       |
 ---------      ------------------------       ------------------
| id |  1 |    | id | chat_id | user_id |     | id | external_id | 
 ---- ----      ---- --------- ---------       ---- -------------
               | 1  |    1    |    1    |     |  1 |     111     |
               | 2  |    1    |    2    |     |  2 |     222     |
                ---- --------- ---------       ---- -------------

```

I need to select one chat.id FOR TWO `user`s. In the example above, the users 111 and 222 are sharing the `chat.id` 1. What I need is to get as a select result the `chat.id` 1 (as the example above) only once when searching `external_id` 111 and 222.

I found some answer here but they didn't help a lot... I always get other chat.id values.

If you need any extra explanation, I'm right here to answer.

Thanks in advance!