Efficiently Selecting Random Rows From a MySQL Table

random_rows

public function getRandomRecords()
{
  // Select the first id in the target table
  $statement = $this->db->prepare("SELECT some_id
  FROM table_name
  ORDER BY some_id ASC LIMIT 1");
  $statement->execute();
  $lowest_id = $statement->fetch(PDO::FETCH_ASSOC);

  // Select the last id in the target table
  $statement = $this->db->prepare("SELECT some_id
  FROM table_name
  ORDER BY some_id DESC LIMIT 1");
  $statement->execute();
  $highest_id = $statement->fetch(PDO::FETCH_ASSOC);

  $records_array = array();

  while(true)
  {
    // Generate a random integer
    $random_id = rand( $lowest_id['some_id'], $highest_id['some_id'] );

    // Check to see if the record exists
    $statement = $this->db->prepare("SELECT col_one, col_two, etc...
    FROM table_name
    WHERE some_id = {$random_id}";
    $statement->execute();
    $result = $statement->fetchAll(PDO::FETCH_ASSOC);

    // If it exists, add it to the array
    if($result) {
      $records_array[] = $record;
    }

    $i++;

    // If the array contains 5 records, stop
    if(count($records_array) == 5) {
      break;
    }
  }

  return $records_array;
}