$query = new Query;
$query->select('ID, City,State,StudentName')
->from('student')
->where(['IsActive' => 1])
->andWhere(['not', ['City' => null]])
->andWhere(['not', ['State' => null]])
->orderBy(['rand()' => SORT_DESC])
->limit(10);
P.S. 2-й результат в выдаче гугла по запросу "yii2 not null"