I have a database and normally users are the central object.
In database I have a tables roles and users in roles so I can give users different permissions on site.
But now I have one doubt.
I saw before one database with structure like this (User is in 1:1 relation to other tables):
User{UserId, Username, Email etc.}
Admin{UserId, some specific columns}
Child{UserId, some specific columns}
Admin{Parent, some specific columns}
and other tables are connected to user not through User table but through Admin, Child and admin.
Because now I design my database I have Users and user can be Admin, CompanyManager and Professor.
I wonder should I design table like I show above or just relied on roles?
What is advantage of the first approach?
And also in my business model User doesn't have to be CompanyManager or Professor so this is actually 1 to 0 or 1 design.
What is a good way to design database with scenario like this?
The advantage of having specific tables for certain types of users is to store information that is only relevant to that class of user.
In your example,
perhaps all users would have a manager - so the manager ID would go in the users column.
managers would have permissions to view certain information, so this would be handled via a role.
only professors would have a Subject, or the "HasTenure" property. So this information would go in a professors table. Using this approach, you avoid the need to have a "Subject" column in the users table, when it is only applicable to a certain subset of users. As such you avoid a functional dependency in the users table, and a violation of 3rd Normal Form.
I prefer this approach:
In this way, you can easily group Roles into categories and assign them to users.
Related
My DB has following tables:
Resource: Some resources can be uploaded on site
Groups: Groups on site
Users: Users on site (not necessarily be part of any group but could be if they like)
Now, when some one uploads a resource then currently, ownership of that resource is given to it's uploader by default. So resource table has column OwnerID with foreign key association to User table.
But now, this has to be changed such that ownership of a resource could be given to either a user or entire group.
I'm trying to decide the migration scheme, to move this owner being user to an entity that could be either user or group. Intuition is that when someone uploads a material, he can choose its owner to be a user or entire group.
Currently my migration plans involves:
Add OwnerType (User, Group, Global) and UserOwner and GroupOwner within the Material table (probably worse normalized table).
OwnerType could be Global if owner is everyone --or-- Group if owner is group entity else user.
Then when I'm querying the Resource table, I can check the OwnerType to condionally select its Owner from either user table or group table.
I do not know if this is good way. I'm using entity framework, and things are already started to look ugly as User and Group hardly have any relationaship that would require me to make generalized entity.
Can some expert guide me on this? What is generally considered good migration plan in this case? Thanks for any help or suggestions.
I'm designing a web application for a school. So far, I'm stuck with the database which has these tables:
users
id
username
password
profile
user_id (FK)
name
last_name
sex
group_id (FK)
(other basic information)
... And other tables irrelevant now, like events, comitees, groups and so on.
So, the users table stores basic information about the login, and the profiles table stores all the personal data about the user.
Now, the *group_id* column in the profile table has a foreign key that references the ID column of the group in which the user is currently enrolled, in the groups table. A user can only be enrolled in one group at once, so there's no need for any additional tables.
The thing is that it doesn't make much sense to me declaring a relation like group HAS MANY profiles. Instead, the relation should be group HAS MANY users, but then, I would have to put a *group_id* column on the users table, which doesn't really fit in, since the users table only stores auth information.
On the other side, I would like to list all the users enrolled in a group using an ORM and getting the a users collection and not profiles. The way I see it, is that the users table is like the 'parent' and the profiles table extends the users table.
The same problem would occur when setting attendances for events. Should I reference the profile as a foreign key in the events_attendance table? Or should I reference the user ID?
Of course both solutions could be implemented and work, but which of them is the best choice?
I have dug a little and found that both solutions would comply with 3NF, so in theory, would be correct, but I'm having a hard time designing the right way my database.
This is a question of your own conventions. You need to decide what is the main entity, right after that you can easiy find a proper solution. Both ways are good, but if you think of User as of the main entity while Profile is a property then you should put GroupId into User, otherwise, if you mean User and Profile as a single entity, you can leave GroupId in Profile, and by this you're not saying group HAS MANY profiles but group HAS MANY users.
By setting a proper one-to-one relation (User-Profile) you can force your data integrity good enough.
My application has several kinds of users with different sets of properties, for example: customers and employees. One user may be belong to more than one of these roles.
So I decided to have this (simplified example) structure of my database:
users (contains the fields applicable to all different kinds of users)
id
username
email
customers (contains fields applicable to customer role)
id
user_id
shipping_address
employees (contains fields applicable to employee role)
id
user_id
salary
Question 1: Is this a good way of handling user roles with many different properties?
In reality I have six roles with sets of 7-20 properties. Some of the roles are not even conventionar roles, but bore like extra properties. If a user decides to login with a Facebook acoount, then the Facebook_account table is applicable.
Question 2: When using an ORM, in my case Eloquent, would it make sense to have the role model (customers) extend the user model?
When I fetch a customer object I really want all user och customer properties together, without having to merge them manually.
I read this on msdn:
Views let different users to see data in different ways, even when they are using the same
data at the same time. This is especially useful when users who have many different interests and skill levels share the same database.
For example, a view can be created that retrieves only the data for the customers with whom an account manager deals. The view can determine which data to retrieve based on the login ID of the account manager who uses the view.
My question:
For the above example , i would have to have a column named Userid/LoginId on my table on which the view is created so that i can apply a check option in the view for this column. and then if a user with a name not in that column tries to enter data , then he/she is blocked.
Yes, you are right. You should
add a column with the user's login or database user name (say you call it username),
each row should have username populated with the login or database name of the person who is allowed to see that row
you can then build a view where you use the builtin functions SUSER_SNAME() (for logins) or USER_NAME (for database names) in your WHERE clause to filter only the rows the user is allowed to see
See Granting Row-Level Permissions in SQL Server (ADO.NET).
You don't have to add a column to the table: it could be more appropriate to instead add a new table to model the relationship.
There's a deisgn rule of thumb that states a table should model an entity or a relationship but not both. Let's say the table in question models the companies a customer owns (i.e. an entity table) and the business rule states the the account manager can only see companies relating to customers he looks after.
Is account manager an attribute of a company? No, so account_manager should not be a column (attribute) in the Companies table.
Is there a direct relationship between account_manager and a company? No, so a relationship table between is not due here (because the relationship is indirect).
Rather, the direct relationships are between account manager and customer, and between customer and company respectively. There should be two tables whose sole purpose is to model these relationships.
You can see my models here:
https://gist.github.com/768947
Just to explain what is happening, I have a few models. At the core of my app, there are: projects, stages, uploads, comments, users. Then there are roles & assignments to manage user authorization.
I am doing this with the plugin declarative_authorization & devise for login.
So the first question is, is it better to just add a column of 'Roles' to my user model/table and store the roles for each user there? If I have a user that has multiple roles, then I can just store all the roles as an array and cycle through them as needed.
Or is it better to do it like I have it setup now, where I use two separate tables and a bunch of joins to setup the assignments? I only have 4 roles: designer, client, admin, superuser.
Better in the sense that it is 'less expensive' from a computing resources standpoint to do each query with the column, than with the joins or is the difference not that significant?
I guess, the root of my question is...right now if I want to get a project assigned to the current_user I simply do current_user.projects.each do |project| and cycle through them that way. This is after I have done: #projects = current_user.projects in the projects controller. The same applies for all my other models - except Users & Roles.
However, if I wanted to find a user with role "client", it becomes convoluted very quickly. Or am I overcomplicating it?
Any help would be appreciated.
I think it's better to have user and role tables that are separate. It's a many-to-many relationship, because a user can have many roles and many users can have the same role. You'll need a JOIN table (e.g. user_role) to do that. I'd recommend three tables. Of course you'll have primary keys for both user and role; the user_role table will have two columns, one for each primary key, and foreign key relationships to their respective tables.
So now if you want all users with the role "client", it's an easy JOIN between user and user_role. If you want a particular user's roles, you'll need to JOIN the three tables.
I would not recommend an array of roles in user. It goes against first normal form.