CREATE TABLE ref_document_types (document_type_code CLOB, document_type_description CLOB)
CREATE TABLE document_drafts (document_id NUMBER, draft_number NUMBER, draft_details CLOB)
CREATE TABLE documents (document_id NUMBER, document_status_code CLOB, document_type_code CLOB, shipping_agent_code CLOB, receipt_date TIME, receipt_number CLOB, other_details CLOB)
CREATE TABLE circulation_history (document_id NUMBER, draft_number NUMBER, copy_number NUMBER, employee_id NUMBER)
CREATE TABLE roles (role_code CLOB, role_description CLOB)
CREATE TABLE ref_document_status (document_status_code CLOB, document_status_description CLOB)
CREATE TABLE draft_copies (document_id NUMBER, draft_number NUMBER, copy_number NUMBER)
CREATE TABLE documents_mailed (document_id NUMBER, mailed_to_address_id NUMBER, mailing_date TIME)
CREATE TABLE addresses (address_id NUMBER, address_details CLOB)
CREATE TABLE ref_shipping_agents (shipping_agent_code CLOB, shipping_agent_name CLOB, shipping_agent_description CLOB)
CREATE TABLE employees (employee_id NUMBER, role_code CLOB, employee_name CLOB, other_details CLOB)

List the employees who have not showed up in any circulation history of documents. List the employee's name.
SELECT employee_name FROM employees EXCEPT SELECT employees.employee_name FROM employees JOIN circulation_history ON circulation_history.employee_id = employees.employee_id
SELECT "employee_name" FROM "employees" EXCEPT SELECT "employees"."employee_name" FROM "employees" JOIN "circulation_history" ON "circulation_history"."employee_id" = "employees"."employee_id"