Максим Осадчий

if(!empty($this->author)){
            $sql = new Expression("(SELECT name FROM book_authors WHERE id = product_book.book_id)");
            $row = (new Query())
                ->from('product_book')
                ->where('product_book.product_id=products.id')
                ->andWhere(['product_book.book_name' => 'book_authors'])
                ->andFilterWhere(['in', $sql, $this->author]);

            $query->andFilterWhere(['exists', $row]);
        }