استفاده از کوئری select با استفاده از createCommand
برای این کار ابتدا باید به دیتابیس متصل شویم

use yii\db\Query;
$connection = \Yii::$app->db;

queryAll

$model = $connection->createCommand('SELECT * FROM tbl_user');
$users = $model->queryAll();

به این صورت که آرایه ای تو در تو از دیتا های موجود را بر می گرداند.

Array
(
    [۰] => Array
        (
            [id] => 1
            [value] => 89.3
            [publish_date] => 2015-08-17 00:00:00
            [picture] => default.jpg
            [user_id] => 1
        )
    [۱] => Array
        (
            [id] => 2
            [value] => 88.4
            [publish_date] => 2015-09-03 00:00:00
            [picture] => default.jpg
            [user_id] => 1
        )
    [۲] => Array
        (
            [id] => 3
            [value] => 87.7
            [publish_date] => 2015-09-11 00:00:00
            [picture] => default.jpg
            [user_id] => 1
        )
    [۳] => Array
        (
            [id] => 4
            [value] => 88.4
            [publish_date] => 2015-09-20 00:00:00
            [picture] => default.jpg
            [user_id] => 1
        )
    [۴] => Array
        (
            [id] => 5
            [value] => 87.3
            [publish_date] => 2015-09-25 00:00:00
            [picture] => default.jpg
            [user_id] => 1
        )
    [۵] => Array
        (
            [id] => 6
            [value] => 87.9
            [publish_date] => 2015-10-01 00:00:00
            [picture] => default.jpg
            [user_id] => 1
        )
    [۶] => Array
        (
            [id] => 7
            [value] => 87.5
            [publish_date] => 2015-10-08 00:00:00
            [picture] => default.jpg
            [user_id] => 1
      )  
    [۷] => Array
        (
            [id] => 8
            [value] => 89.300
            [publish_date] => 2015-10-15 00:00:00
            [picture] => default.jpg
            [user_id] => 1
        )
    [۸] => Array
        (
            [id] => 9
            [value] => 86
            [publish_date] => 2015-10-24 00:00:00
            [picture] => default.jpg
            [user_id] => 1
        )
    [۹] => Array
        (
            [id] => 10
            [value] => 86.900
            [publish_date] => 2015-10-30 00:00:00
            [picture] => default.jpg
            [user_id] => 1
        )
)

queryOne

$model = $connection->createCommand("SELECT * FROM tbl_user where userid=$id");
$users = $model->queryOne();

فقط یک رکورد بر می گرداند البته به صورت آرایه

Array
(
    [id] => 1
    [value] => 89.3
    [publish_date] => 2015-08-17 00:00:00
    [picture] => default.jpg
    [user_id] => 1
)

queryColumn

$model = $connection->createCommand('SELECT value FROM weight');
$users = $model->queryColumn();

فقط ستون صدا زده شده را در آرایه نمایش می دهد

Array
(
    [۰] => ۸۹٫۳
    [۱] => ۸۸٫۴
    [۲] => ۸۷٫۷
    [۳] => ۸۸٫۴
    [۴] => ۸۷٫۳
    [۵] => ۸۷٫۹
    [۶] => ۸۷٫۵
    [۷] => ۸۹٫۳۰۰
    [۸] => ۸۶
    [۹] => ۸۶٫۹۰۰
)

queryScalar

$model = $connection->createCommand('SELECT COUNT(*) FROM weight');
                $weight = $model->queryScalar();

فقط عدد بر می گرداند .
برای sum , max نیز استفاده می شود