How to Retrieve Associative Arrays Grouped by Column Values with PDO?

Retrieving Associative Array Grouped by Column Values with PDO

Problem:
To efficiently organize a dataset into an associative array grouped by the values of a specified column, there is a need to find a way to bypass the unnecessary nesting level when using PDO's FETCH_GROUP|PDO::FETCH_ASSOC mode.

Solution:
By leveraging the combination of PDO::FETCH_GROUP and PDO::FETCH_UNIQUE modes, the desired array structure can be achieved with a single fetch operation.

The code snippet below demonstrates this approach:

<code class="php">$stmt = $pdo->query('SELECT * FROM employee');
$result = $stmt->fetchAll(\PDO::FETCH_GROUP|\PDO::FETCH_UNIQUE);</code>

The PDO::FETCH_GROUP mode groups the rows by the values of the first column, while PDO::FETCH_UNIQUE ensures that only the first row for each unique group value is included in the result.

As a result, the $result array will contain the following structure:

<code class="php">Array
(
    [Antony] => Array
        (
            [age] => 34
            [sex] => M
            [position] => programmer
        )

    [Sally] => Array
        (
            [age] => 30
            [sex] => F
            [position] => manager
        )

    [Matthew] => Array
        (
            [age] => 28
            [sex] => M
            [position] => designer
        )
)</code>

This eliminates the unnecessary nesting level encountered when using PDO::FETCH_GROUP|PDO::FETCH_ASSOC alone, providing a more efficient and straightforward way to retrieve associative arrays grouped by column values.

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