Database Design for a Multiplayer/Single Quiz game - mysql

Question

I saw a lot of questions here but no one fits with my problem. I'm trying to create an ER model scalable, and if I want to add more data don't break almost anything, so what I've trying to create is :
There are 2 types of users, let's say Admin and Worker, and they have different roles.
Admin can do a CRUD of questions, and also can create a room where the users can join to play together (this is just a name, something like Kahoot! does) but maybe is a good idea to create more attributes inside of it like, WHO is playing in this room, POINTS for everyone but let's talk it afterwards when I show you the design.
Ok the thing is, on my design I have :
Table User which contains :
_id
username
password
date_creation
This is a default one, but then I'm wondering how do I define the Role if it's an Admin or a Worker, something like isAdmin:true and then I check this Bool? Or I can create another table that is Role and connect it to User table?
But maybe I have to create a table for both, I mean there's an Admin which has a password, and some functionalities and then ther'es the user Worker which has another password and another functionalities.
Then I'd like to have the Question table where contains :
_id
question_name
answers[1,2,3,4]
correctAnswer or answers because it can be multi option chooser
topic
isExamQuestion
dificulty
Then the Room table should contains :
_id
name
capacity
type (game can be as a group or solo) that's why this attribute
exam (This should be a flag to know if this question is for an exam or not (It can be for EXAM or PRACTISE)
ranking (This is the top X from 1 to X)
don't think if I have to add the winner here because if I get the position 0 from ranking I get the winner...
There's a table named Topic as well, if my question have a topic then I can select the question by Topic. An example of Topic should be Math so user can do only exams or do tests with math questions.
_id
Name
Questions[...]
Then I have to store like a historic about what are the questions worker has answered correct and what did not, to make some statistics, but I need to store some historicals for Admin to see in this topic the average that Workers have failed more is : Question23 (for instance) something like that.
What I'm missing, could you try to help me to figure it out how to make this design better?
NOTE : I'm using Spring for server side, Angular for Frontend stuff, and Android for App, I can change anything to work faster/better with this database though.
EDIT
There's the flow of the game if you need more details and if I'm explainted wrong .
Admin flow
Create questions (with different kinds of answers like True/false, with a checkbos (single and multianswer), text, etc...)
Create a "game" where workers can join (This is mostly programming stuff) but it should be a room with attributes there, like id of the room, maxNumber, type (exam), and store historicals, theres also a type of game (for instance, images, videos, etc..)
See statistics about Workers it means see how many answers they answered correct, failed, see per topic (This is like joins and stuff, but the design has to be good done)
See historic of the exams that he did before with all of the information (participant, score, time, stuff)
And the Worker flow is
He can practise means that he's answering questions randomly or by topic (every single answer should be saved for statistics and to avoid repeat the ones he respons correct), also he can do exams (not multiplayer) just an option that Admin can check if the question is part of an exam or not.
And then the room stuff, he can join with the Id.
If you need further clarification let me know and I'll reply you as soon as possible.

Answer 1

In fact, your system has three logical parts (modules):
users module that contains user data and implements authentication and the authorization of user actions
questionnaires module that includes management of questions and answer
questionnaires history module that contains history by each user
Database design of those modules can look as follows
USER MODULE:
role - contains user roles in the system
id - unique identifier of the role
name - the role name, for example, admin, worker, etc.
user - contains users and information about roles were assigned to them
id - unique identifier of the user
username
password
role_id - identifier the role was assigned to the user
QUESTIONNAIRES MODULE:
topic - contains question themes
id - unique identifier of the theme
name - a name of the theme
question - contains questions
id - unique identifier of the question
topic_id - topic identifier of the question
text - content of the question
is_exam_question - exam question or not
type - type of answers (boolean, checkboxes or etc.)
difficulty
answer - contains all answers of questions
id - unique identifier of the answer
question_id - identifier of the question that contains the answer
text - content of the question
is_correct - flag that means the answer is true or false
room - contains information about rooms
id - unique identifier of the rum
name - name of the rum
capacity - the maximum number of workers which can join to the room
type - room type: group, solo or etc.
learing_type - room type: exam, practice or etc.
user_in_room - contains information about users which were joined to the room
user_id - identifier of the user that was joined to the room
room_id - identifier of the room
score - current score of the user in the room
HISTORY MODULE:
user_question_history - contains information about questions which were answered by the user
user_id - identifier of the user
room_id - identifier of the room where the user answered questions
question_id - identifier of the question that was answered by the user
score - user score by the question
user_answer_history - contains information about answers which were chosen by the user
user_id - identifier of the user
room_id - identifier of the room where the user answered questions
question_id - identifier of the question that was answered by the user
answer_id - identifier of the answer that was chosen the user
Usage of this schema gives the ability to build different reports. For example, you can display the result of all users by room
SELECT r.id,
r.name,
u.username,
ur.score
FROM room as r
LEFT JOIN user_in_room as ur ON ur.room_id = r.id
LEFT JOIN user as u ON u.id = ur.user_id
WHERE r.id = <id>
Or you can see detail information about answers of the user
SELECT
q.text,
a.text
FROM user_in_room as ur ON ur.room_id = r.id
LEFT JOIN user_question_history as uqh ON ugh.user_id = ur.user_id AND ugh.root_id = ur.room_id
LEFT JOIN question as q ON q.id = ugh.question_id
LEFT JOIN user_answer_history as uah ON uah.user_id = ugh.user_id AND uah.room_id = ugh.room_id AND uah.question_id = ugh.question_id
LEFT JOIN answer as a ON a.id = uah.answer_id
WHERE ur.room_id = <id> AND ur.user_id = <id>

Answer 2

Honestly, if you're certain you'll only have to possible types--both now and in the future--a simple bool isAdmin in your user table will work nicely. Everything else the admin does can be handled from the programming side. No need to clog up your db.
That said, if there's even a small chance you will have other types of users in the future, Maxim's answer is the way to go. That way, adding another role such as "Editor," for instance, is a simple as adding a record to the "Role" table. In fact, adding 1000 new types users is as simple as adding records to your "Role" table. Because you already have a table that you look to for the role, your code doesn't have to worry about all the possible types of users (which is a pain if you have a lot of them), only the ones it needs. The db is handling the rest.
One drawback to Maxim's answer is that it takes more work to implement in the db, and more work to view/update the role of the user.
To implement in the db, you need to create a whole extra table and make sure it's linked properly. This isn't hard, but, especially if you're new to dbs, is extra work that might not be worth it to you. This also means, from a maintenance side, that you have another table to keep tabs on. Not a huge deal, but, again, something to think about.
From the code side, this creates extra chores as well. For one, the user type is no longer directly in your users table--an ID is. This means when you want to know the name of the user type, you will have to either a) query the db for that user type based on the ID you have, or b) join the 2 tables, which can be tricky at times. Updating the role also has similar chores.
Again, these aren't huge problems, just things to think about. It might not be worth the extra work if you will only have two possible options.
So, in short, a boolean will work and is simple to implement, but is not scalable. Maxim's answer is quite scalable and makes future expansion easier, but somewhat harder to implement and maintain. You'll have to make the decision what you prefer.

Answer 3

You need a Profile table with one-to-many with User table, this way if another privelege you want to apply, just add new profile entry:
User table:
Id
Username
Fullname
Profile_id
...
Profile table:
Id
Name
Description
Exam and Question tables are related with many-to-many, to break it you will have a third table Question_Exam:
Question_Exam:
id_exam
Id_Question
Answer(provided)
Id_user(taking the exam)
IsCorrect(boolean, to avoid farther queries )
date
Topic and Question are one-to-many
Question table:
Id
Name
Answer(The correct one)
Id_topic
The other structure is fine.