$query="SET @laboratory_prefix_id = 5;
    SET @min_sample_number = 1;
    (
        SELECT @count
        FROM sample, (select @count := @min_sample_number-1) dummy
        WHERE sample.laboratory_prefix_id = @laboratory_prefix_id
          AND sample.sample_number > @min_sample_number-1
          AND (@count := @count+1) < sample.sample_number
        ORDER BY sample.sample_number ASC
        LIMIT 1
    )
    UNION ALL
    (
        SELECT @min_sample_number
    )
    ORDER BY 1 DESC
    LIMIT 1;";
$rows = Yii::$app->db->createCommand($query)->queryAll();

$rows = Yii::$app->db->createCommand('SET @laboratory_prefix_id = 5;')->execute();
    $rows = Yii::$app->db->createCommand('SET @min_sample_number = 1;')->execute();
    $rows = Yii::$app->db->createCommand($query)->queryAll();

(
    SELECT @count
    FROM sample, (select @laboratory_prefix_id := ?
                       , @min_sample_number := ?
                       , @count := @min_sample_number-1) dummy
    WHERE sample.laboratory_prefix_id = @laboratory_prefix_id
      AND sample.sample_number > @min_sample_number-1
      AND (@count := @count+1) < sample.sample_number
    ORDER BY sample.sample_number ASC
    LIMIT 1
)
UNION ALL
(
    SELECT @min_sample_number
)
ORDER BY 1 DESC
LIMIT 1;

$rows = Yii::$app->db->createCommand('SET @laboratory_prefix_id = 5;')->execute();
$rows = Yii::$app->db->createCommand('SET @min_sample_number = 1;')->execute();
$rows = Yii::$app->db->createCommand($query)->queryAll();