在SQL中缓慢更改数据

Question

My question is regarding the best way to implement a case of slowly changing data in MS SQL Express 2014.

The scenario is as follows:

An administrator makes and defines tests, which users take. The administrator has one table called "Questions", which has all questions possible.

Another table called "Quiz" identifies 10 questions from the Questions table to define a Quiz.

Another table called "Quiz Definition" identifies how each of the 10 questions in the Quizzes table should be formatted (Short answer, or paragraph response).

Another table called "Administration Configuration" basically assigns a Quiz to a Quiz definition, which then gets administered to a user.

The end user wishes to be able to change parameters in any of these tables over time. So for example, an administrator may want to change a question from "How are you doing?" to "How are you doing today?".

My issue is, say I administer a test today where the question ID 1234 was "How are you doing?". Tomorrow, I change the question, and the day after, I administer the test as "How are you doing today?". If I rely on purely relational look-ups to ask what question was asked to the user, I will see that question ID 1234 was asked. But the first test subject was asked the first version of the question, while the second user was asked the second version.

My question is, given this case, what is the best technique to 1) allow the administrator to edit records in the database while 2) maintaining "point in time" data for the test results so I know exactly how each test was executed? All I could come up with so far was maintaining a massive "test results" table that listed the question, question type, etc. in the same row as every result. The issue with that method is that there may be a lot of parameters to keep track of in the actual application, making the results table like 30 columns wide.

Answer 1

Make a new table (foo) which saves the history of questions revisions. foo table has ID, questionId and questionBody. Also in test results you should save foo.ID . No more changes needed in Quiz definition.

Answer 2

You need to change the data model.

A test is a test with a set of questions, and the questions have a history that grows with any change.

So, your test will address the questions with a defined version (history id). If you change the test, it will make sense, to give the test a history as well.

Update: If you cannot change test and question, you could create a test-history table and a question-history table and testquestion history. On changing the question, you duplicate the test, question, links into history table. Then modify the question and update the test histody. This is not very nice and will duplicate a lot of data. Also, xou will need special code to extract and handle display of historic test. It is better imho, to have a combined fk, made from id and version. when updating the question, you update the hist version of test, have an n:m table ready with test-question relation and duplicate the links to the questions. then update the single question by duplicating it, changing version and text creating a new version and link it to the new test, replacing the old version.

The importance of question.id in your system is unknown. if it is not relevant, you need to version only test. A new version of a question then has no connection with the old version.