Now the canteen management asked to

Now the canteen management asked to increase the face recognition function, that is, students can brush both IC card, can also brush face meal. The change of demand in this case is a "one-sided action" . The case is not precise. The case needs to change the business attribute of an existing field and change the relation between the tables, because the face recognition function needs to be added You have to create a new table to store the data, you have to add new fields to the original table, and then you have to add a new table-to-table association that is directly related to the structure of the functional logic Once the relationship changes, it means that all the related functions need to be structurally changed, and the database structure will be reorganized, which will be a very painful change. The impact on historical data will be more troubling because changes to the association relationships between tables will involve a large amount of historical data that was previously the product of specific functional logic It is organized according to a specific database structure. Once a change in demand occurs, the newly generated data is organized and stored in a new way, which may not be consistent with the previous historical data At this point, the existing historical data will become an unavoidable problem. How to solve the demand change, the method is as follows: In the database in the student information table to add the face input, delete, change. At the same time, for the historical data, we need to connect the new face data to the previous IC card and the students'personal information, so that the newly added data can communicate with the previous information to achieve a one-to-one relationship.