Merge Statement Syntax

MERGE INTO employees e
    USING (SELECT * FROM hr_records WHERE start_date > ADD_MONTHS(SYSDATE, -1)) h
    ON (e.id = h.emp_id)
  WHEN MATCHED THEN
    UPDATE SET e.address = h.address
  WHEN NOT MATCHED THEN
    INSERT (id, address)
    VALUES (h.emp_id, h.address);