input: Write a function to select all rows from a table where the 'status' is 'approved'. Define the function to execute the query and return the result.
  assert select_approved_rows(table_name="orders", cur=cur) == [(1, 'Item A', 'approved'), (3, 'Item C', 'approved')]
  assert select_approved_rows(table_name="items", cur=cur) == []
  assert select_approved_rows(table_name="logs", cur=cur) == [(9, 'Log 9', 'approved')]
  assert select_approved_rows(table_name="", cur=cur) == []
output: def select_approved_rows(table_name, cur):
      if not table_name:
          return []
      cur.execute(f"SELECT * FROM {table_name} WHERE status = 'approved'")
      return cur.fetchall()