mysql 8.0 ,游标创建ok, 但执行“open”总是报错，请教大家该如何解决？

mysql> create procedure processorders()
    -> begin
    -> DECLARE ordernumbers CURSOR
    -> FOR
    -> SELECT order_num from orders;
    -> end //
Query OK, 0 rows affected (0.02 sec)
```创建游标过程无问题。

```sql
mysql> open ordernumbers;
ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'open ordernumbers' at line 1

之后执行open操作，一直报错。
百度没有找到有效的解决办法，直接去翻看SQL官方文档也搞不清是哪里写错了。