I have 3 tables, one which stores pictures and one that stores votes for pictures (`pictures` and `picture_votes`). The last table is `categories`, which stores the different categories a picture can belong to.

Here are the tables (non-relevant columns omitted);

```
- Table `pictures`
picture_id  INT
category_id INT

```

and

```
- Table `picture_votes`
vote        TINYINT
picture_id  INT

```

and finally

```
- Table `categories`
category_id INT

```

**What I want to do** is to select the top 3 most voted pictures for *each* category. 

I'm really lost and don't know how to do this most effectively..