I have 3 tables users , roles and roles_users. The roles_users table have user_id and role_id
Now my models are Model_User, Model_Role, Model_User_Role.
How can i link the three models so that every user is associated to one role and one role has many users.
I am using ORM and i want to display the list of users with the name of there role.
Note: The table i have taken from Auth Module of Kohana.
You can use $_belongs_to, $_has_one and $_has_many arrays to set relationship between the models.
Kohana 3 :: ORM Relationships
I did a many to many relation with roles and users. And will write business logic that a users will not have more than one roles.
Related
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.
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.
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.
If I a many-to-many relationship between Users and Roles and I have an instance of a User entity and several Role Ids can I insert a relationship between the two types of entities without having any other Role data and without doing a select on the Roles first?
Update:
I might not have been clear enough. I don't have an instance of a Role, only the role id. Is it possible to create the relationship between User and Role without filling a Role object from the database first?
Yes if you have the IDs and you need to relate them
You should be able to do this (pseudo code)
// how you get this doesn't matter so long as it is in the Context
User user = ...;
Role role = new Role {Id = 2};
// role 2 is in unchanged state
ctx.AttachTo("Roles", role);
// role 2 is unchanged + added relationship between user and role 2
user.Roles.Add(role);
ctx.SaveChanges();
The key here is that AttachTo puts an entity into the ObjectState manager in the unchanged state. So long as you don't need to modify that entity, and only use if for relationship building, you don't even need to know all the property values, the PK is sufficient.
Once you have it attached you can then build the relationship.
Hope this helps
Cheers
Alex
If you're not using databinding, sure. Many to many gets mapped as list of references to each other. User.Roles.Add(Role ...) should be fine.
So I have a database schema like this:
Users
UserId
RoleUserXRef
RoleUserId
RoleId
UserId
Roles
RoleId
Name
With foreign keys defined between User & RoleUserXRef and RoleUserXRef & Role. Basically, I have a one to many relationship between users and roles.
How would I model this in dbml, such that the generated User class has a list of Roles that the user has assigned to them?
Creating a many-to-many releationship via simple DBML manipulation is not supported currently. You can extend the partial class to manually create properties, if you really want that sort of functionality "built in".