SQL display and fetch GROUP BY categories - php

Question

I have a list of authors and I would like to display it by book genre, like this:
Horror
Stephen King
Author 2
Author 3
...
Comedy
Author 4
Author 5
...
In my database I have an author table:
t_author
aut_name | aut_genre
Stephen King | 1
...
...
Author 4 | 2
And a genre table :
t_genre
genre_id | genre_name
1 | Horror
2 | Comedy
...
...
I've tried to use a GROUP BY but I can't find how to display the names of the category and organize my list:
SELECT t_author.aut_name, t_author.aut_genre
FROM t_author
LEFT JOIN t_genre ON t_author.aut_genre = t_genre.genre_id
GROUP BY t_genre.aut_genre
So, using MySQL and PDO, is there a way to select and fetch all the authors and display it by categories?
No need to say that I'm not looking for a code but just a clue because I don't even see how to describe it. I mean, is GROUP BY the right statement to use?
EDIT 1 :
Apparently, I was looking for something like this :
SELECT t_author.aut_name, t_author.aut_slug, t_genre.genre_name
FROM t_author
LEFT JOIN t_genre ON t_author.genre_id = t_genre.genre_id
But it displays:
Horror
Stephen King
Horror
Author 2
Comedy
Author 4
Horror
Author 3
I perfectly understand why but I can't find how to display it like below:
Horror
Stephen King
Author 2
Author 3
...
Comedy
Author 4
Author 5
...
Answer
HtmHell provided me a good way to do this with a 2D array. For my 3D array, I edited his code like this:
foreach($result as $author=> $slug) {
$authorsByGenre[$slug['genre_name']][] = array($slug['aut_name'] => $slug['aut_slug']);
}
return $authorsByGenre;

Answer 1

How about something like this:
$authorsByGenre = [];
$results = $db->query("
SELECT t_author.aut_name, t_genre.genre_name
FROM t_genre
JOIN t_author
ON t_author.aut_genre = t_genre.genre_id
")->fetchAll();
foreach ($results as $data) {
$authorsByGenre[$data['genre_name']][] = $data['aut_name'];
}
print_r($authorsByGenre);

Answer 2

SELECT GROUP_CONCAT(t_author.aut_name) as authors, t_genre.genre_name as genre FROM t_author
LEFT JOIN t_genre ON t_author.aut_genre = t_genre.genre_id
GROUP BY t_author.aut_genre
This will output authors as author1,author2,author3 in column 1 and genre column with genre_name so you can split or explode authors or whatever

Answer 3

Like it was suggested in the comments, PDO::FETCH_GROUP is the answer to your question. Dunno why you ignored it
$sql = "SELECT genre_name, aut_name, aut_slug
FROM t_author a LEFT JOIN t_genre g ON a.genre_id = g.genre_id";
$authorsByGenre = $db->query($sql)->fetchAll(PDO::FETCH_GROUP);
print_r($authorsByGenre);