2. Choose books. Book titles, books. Pricing, publishing house. The name of the publishing house comes from books, the classification of books where the publishing house is located =' teaching materials' and books. Publishing house number = publishing house. Publishing house number;
3. Select the publishing house number, count (book number) and avg (pricing) from the book group through the publishing house number;
4. Choose books. Book number, title and publisher, in which book classification = "textbook" and books. Press number = press. Press the number, and then press. Press number =' Higher Education Press' and books. Pricing > 30;