$model = User::findOne(['id' => 1]);

$model = User::find('username','email')->where('id'=1)

$model = User::find()
           ->select('column1, column2')
           ->where(['id' => $id])
           ->one();

echo $model->column1;

$model = User::find()->select(['username','email'])->where('id=1')->One();

$model = User::find()->select(['username','email'])->where('id=:id', [ ':id' => 1 ])->One();

$model = User::find()
       ->select(['column1', 'column2'])
       ->where(['id' => $id])
       ->one();

$model = User::find()->select(['username','email'])->where('id=1')->One();