SELECT budget_type_code ,  count(*) FROM Documents_with_expenses GROUP BY budget_type_code
Show budget type codes and the number of documents in each budget type.
[Schema (values) (types)]: | cre_Docs_and_Epenses |  Ref_Document_Types : document_type_code (text) , document_type_name (text) , document_type_description (text) | Ref_Budget_Codes : budget_type_code (text) , budget_type_description (text) | Projects : project_id (text) , project_details (text) | Documents : document_id (text) , document_type_code (text) , project_id (text) , document_date (text) , document_name (text) , document_description (text) , other_details (number) | Statements : statement_id (text) , statement_details (text) | Documents_with_Expenses : document_id (text) , budget_type_code (text) , document_details (text) | Accounts : account_id (text) , statement_id (text) , account_details (text);