另外，如前面的例子所示，在采用这种方式时对于键不能使用数字，否则会导致抛出一个异常。

In addition, you can't use Numbers for the keys in this approach, as shown in the previous example. Doing so causes an exception to be thrown.

youdao

每个移植文件开始的序列数都比前面的移植文件大，并且该数字符合位于数据库特殊表中的方案版本。

Each migration file starts with a sequence number one greater than the previous migration file, and that number corresponds to the schema version kept in a special table in the database.

youdao

这个显示数字必须与在前面的配置步骤中所用的数字相匹配。

The display number must match the one you are prompted with in the previous configuration step.

youdao

Just point at the start of this list, and this one so which number comes first?

指向列表的开始处，对于它来说,哪个数字在前面？

哈佛公开课 - 计算机科学课程节选