sql 更改Table 字段名称长度类型

更改column时有可能遇到问题。貌似权限问题：

saving changes is not permitted. The changes you have made require the following tables to be dropped and re-created. you have either made changes to a table that can't be re-created or enabled the option prevent saving changes that require the table to be re-created.

执行类似语句可以解决：