I have a table called `test_db` and I want to delete all but one from the duplicates of the `names` column, this is my database:

```
ID | Names
---+------
1  | Phil
2  | John
3  | John
4  | James
5  | Phil
6  | Robert

```

And I want to keep this:

```
ID | Names
---+------
1  | Phil
2  | John
4  | James
6  | Robert

```