I have the following structure in the table:

```
id | name     | descr
1  | BMW      | asafsf saf
2  | Audi     | asafsf saf
3  | Audi     | asafsf saf
4  | Porsche  | asafsf saf
5  | Mercedes | asafsf saf
6  | Mercedes | asafsf saf
7  | Audi     | asafsf saf

```

I would like to grab all the companies that have only one record in the table, so in this case, the output would be like:

```
1  | BMW      | asafsf saf
4  | Porsche  | asafsf saf

```

How could this be done (I've tried grouping, but that will also scrap other companies with multiple rows in the table)?

PS: I am using Ruby On Rails, so maybe there is a method in ActiveRecord for that.

Thank you in advance.