CREATE TABLE accounts (account_id DECIMAL, statement_id DECIMAL, account_details TEXT)
CREATE TABLE statements (statement_id DECIMAL, statement_details TEXT)
CREATE TABLE documents_with_expenses (document_id DECIMAL, budget_type_code TEXT, document_details TEXT)
CREATE TABLE ref_budget_codes (budget_type_code TEXT, budget_type_description TEXT)
CREATE TABLE projects (project_id DECIMAL, project_details TEXT)
CREATE TABLE documents (document_id DECIMAL, document_type_code TEXT, project_id DECIMAL, document_date TIME, document_name TEXT, document_description TEXT, other_details TEXT)
CREATE TABLE ref_document_types (document_type_code TEXT, document_type_name TEXT, document_type_description TEXT)

Show the ids for projects with at least 2 documents.
SELECT project_id FROM documents GROUP BY project_id HAVING COUNT(*) >= 2
SELECT "project_id" FROM "documents" GROUP BY "project_id" HAVING COUNT(*) >= 2