如果要创建外键，它必须引用主键或具有唯一约束的字段.

If you want to create a foreign key, it must reference either the primary key, or a field with a unique constraint.

如果你想显示客户的名字，让外键引用CustomerID，然后用join来显示结果.

If you want to display the customer's name, make the foreign key reference the CustomerID, and display the results with a join.