数据库已被告知要确保数据完整性.这就是你所看到的.有参考一个国家的调查数据.如果您删除国家/地区表，则调查数据将没有与之关联的有效国家/地区.您必须先删除调查，然后才能删除国家/地区.

The database has been told to ensure data integrity. This is what you're seeing. There is survey data that references a country. If you delete the country table then the survey data won't have valid countries associated with it. You'll have to remove the surveys first before you can remove the countries.