What is the document type name for the document with name "How to read a book"?
create table ref_document_types (document_type_name varchar, document_type_code varchar, PRIMARY KEY (document_type_name)); create table all_documents (document_type_code varchar, document_name varchar, PRIMARY KEY (document_type_code))
select t2.document_type_name from all_documents as t1 join ref_document_types as t2 on t1.document_type_code = t2.document_type_code where t1.document_name = "how to read a book"