Is there a way to fetch associative array grouped by the values of a specified column with PDO?

Question

For example, let\'s use some simple data set

+---------+------+------+------------+
| name    | age  | sex  | position   |
+---------+------+------+---------         


        

Answer 1

It doesn't look like anyone has mentioned this variation, so, for the benefit of future Googlers:

Combine the \PDO::FETCH_GROUP and \PDO::FETCH_COLUMN flags. This vastly simplified my SQL statement and returned the exact result set I wanted. It's fast, too.

$this->database->query('SELECT t.fk, t.id FROM my_table t ORDER BY t.fk ASC, t.id ASC')
  ->fetchAll(\PDO::FETCH_GROUP|\PDO::FETCH_COLUMN);

Where t.fk has a one-to-many relationship with t.id.

I didn't have to concern myself with a GROUP BY statement or MySQL's finicky handling of grouping on multiple fields. Best of all, I received results in the form of:

[
  foreign_key_1 => [
    0 => 11111,
    1 => 22222,
    2 => 33333,
  ],
  foreign_key_2 => [
    0 => 44444,
    1 => 55555,
    2 => 66666,
  ],
  foreign_key_3 => [
    0 => 77777,
    1 => 88888,
    2 => 99999,
  ],
];

Rather than:

[      
  foreign_key_1 => [
    0 => [
      id => 11111,
    ],
    1 => [
      id => 22222,
    ],
    2 => [
      id => 33333,
    ],
  ],
  foreign_key_2 => [
    0 => [
      id => 44444,
    ],
    1 => [
      id => 55555,
    ],
    2 => [
      id => 66666,
    ],
  ],
  foreign_key_3 => [
    0 => [
      id => 77777,
    ],
    1 => [
      id => 88888,
    ],
    2 => [
      id => 99999,
    ],
  ],

];

Hope it helps someone out there!

---

For reference: https://phpdelusions.net/pdo/fetch_modes

Answer 2

Key assoc array

PDO::FETCH_GROUP|PDO::FETCH_UNIQUE|PDO::FETCH_ASSOC