Question

I have MySQL query that selects user names and theirs knowledge (may be more than one).

It returns something like this…

array(5) {
  [0]=>
  array(5) {
    ["user_id"]=>
    string(2) "30"
    ["name"]=>
    string(6) "foo1"
    ["knowledge"]=>
    string(15) "Basic Materials"
  }
  [1]=>
  array(5) {
    ["user_id"]=>
    string(2) "33"
    ["name"]=>
    string(6) "foo2"
    ["knowledge"]=>
    string(15) "Basic Materials"
  }
  [2]=>
  array(5) {
    ["user_id"]=>
    string(2) "34"
    ["name"]=>
    string(10) "foo3"
    ["knowledge"]=>
    string(9) "Eating"
  }
  [3]=>
  array(5) {
    ["user_id"]=>
    string(2) "34"
    ["name"]=>
    string(10) "foo3"
    ["knowledge"]=>
    string(9) "Financial"
  }
  [4]=>
  array(5) {
    ["user_id"]=>
    string(2) "34"
    ["name"]=>
    string(10) "foo3"
    ["knowledge"]=>
    string(8) "Services"
  }
}

As you can see, in this example, it does returns five entries. However, three of them have duplicate IDs (and names). I’m looking for a way to return only three entries like this…

Is it possible to do in the query?

array(5) {
  [0]=>
  array(5) {
    ["user_id"]=>
    string(2) "30"
    ["name"]=>
    string(6) "foo1"
    ["knowledges"]=>
    array(1) {
        [0] => string(15) "Basic Materials"
    }
  }
  [1]=>
  array(5) {
    ["user_id"]=>
    string(2) "33"
    ["name"]=>
    string(6) "foo2"
    ["knowledges"]=>
    array(1) {
        [0] => string(15) "Basic Materials"
    }
  }
  [2]=>
  array(5) {
    ["user_id"]=>
    string(2) "34"
    ["name"]=>
    string(10) "foo3"
    ["knowledges"]=>
    array(1) {
        [0] => string(15) "Eating"
        [1] => string(15) "Financial"
        [2] => string(15) "Services"
    }
  }
}

Other option I see is to process results on server-side.

Here is how the query looks like:

SELECT `profiles`.`user_id`, `users`.`name`, `users`.`surname`, `users`.`country`, `profile_knowledges`.`knowledge`
FROM `profiles`
JOIN `users`
ON (`users`.`id` = `profiles`.`user_id`)
JOIN `profile_knowledges`
ON (`profile_knowledges`.`profile_id` = `profiles`.`id`)

Answer 1

For this particular case you could write something like this:

$users = array();

while ($row = /* fetch a single row from result set */) {
    if (isset($users[$row['user_id']]) == false) {
        $users[$row['user_id']] = array(
            'id' => $row['user_id'],
            'name' => $row['name'],
            'knowledges' => array()
        );
    }

    $users[$row['user_id']]['knowledges'][] = $row['knowledge'];
}

However it’s a better idea to use an ORM such as Doctrine to handle such situations.