Below is the list of tables from the database along with their columns and datatype. Need to generate an accurate SQL query for the question.
Only use the columns present in the respective table. Only use the columns which are required to generate the SQL query. Only use table joins if required and not otherwise.

### Tables ###
TABLE: CREATE TABLE documents ( document_id number, document_type_code text, project_id number, document_date time, document_name text, document_description text, other_details text )
TABLE: CREATE TABLE documents_with_expenses ( document_id number, budget_type_code text, document_details text )
TABLE: CREATE TABLE statements ( statement_id number, statement_details text )
TABLE: CREATE TABLE accounts ( account_id number, statement_id number, account_details text )
TABLE: CREATE TABLE ref_budget_codes ( budget_type_code text, budget_type_description text )
TABLE: CREATE TABLE projects ( project_id number, project_details text )
TABLE: CREATE TABLE ref_document_types ( document_type_code text, document_type_name text, document_type_description text )

### Question ###
How many documents correspond with each project id?

### Accurate SQL ###

SELECT project_id, COUNT(*) FROM documents GROUP BY project_id