Properly joining tables without repeat data - mysql

Question

I am trying to join tables to prevent too many database queries, but I don't like the way the data is returning.
The Query:
SELECT person.name, dog.dog_name FROM person JOIN dog ON person.id = dog.person_id
The return looks like this:
Array
(
[0] => Array
(
[name] => Jim
[dog_name] => Wolf
)
[1] => Array
(
[name] => Jim
[dog_name] => Frisky
)
[2] => Array
(
[name] => Tina
[dog_name] => Pokedot
)
[3] => Array
(
[name] => Tina
[dog_name] => Spiky
)
)
Is it possible to have the query instead return something like:
Array
(
[0] => Array
(
[name] => Jim
[dog_name] => array(Wolf, Frisky)
)
[1] => Array
(
[name] => Tina
[dog_name] => array(Pokedot, Spiky)
)
)

Answer 1

The closest solution is:
SELECT person.name, GROUP_CONCAT(dog.dog_name) AS dog_names
FROM person JOIN dog ON person.id = dog.person_id
GROUP BY person.id
This returns a string which is a comma-separated list of dog names, not a PHP array. You'll have to explode() that string in application code.
Note that the default length limit for GROUP_CONCAT() is 1024 characters, and it is controlled by the configuration option group_concat_max_len.
I agree with the comment from #KonstantinWeitz, it's worthwhile to let the RDBMS do what it's best at, and then use PHP code to post-process the results into a format you want.
For example, here's how I'd do it to return the array you described:
$peoplesdogs = array();
$stmt = $pdo->query("SELECT person.name, dog.dog_name FROM person JOIN dog ON person.id = dog.person_id");
while ($row = $stmt->fetch(PDO::FETCH_ASSOC)) {
$peoplesdogs[$row["name"]]["name"] = $row["name"];
$peoplesdogs[$row["name"]]["dog_name"][] = $row["dog_name"];
}
return array_values($peoplesdogs);