Relation between users with messages - sql

Question

I have a table of Users:
create table dbo.User
(
Id int identity not null,
Name nvarchar (400) null,
// Other coluns as Login, Password, etc.
)
create table dbo.Role
(
Id int identity not null,
Name nvarchar (20) null
)
create table dbo.UserRole
(
UserId int not null,
RoleId int not null
)
Each user has one or more roles.
I need to relate users one to each other in periods of type.
For example, one professor to its students during 4 months in 2015.
And I also need to track messages between users.
One of my ideas would be the following:
create table dbo.UserToUser
(
FirstUserId int not null,
SecondUserId int not null,
StartDate datetime not null,
EndDate datetime not null
)
Being both FirstUserId and SecondUserId FK's of Users table.
create table dbo.Message
(
ToId int not null,
FromId int not null,
Text nvarchar(max) not null,
Created datetime not null
)
Being both ToId and FromId FK's of Users table.
Should this be done in another way?

Answer 1

This seems fine but you could be more generic with the relationships. For example you might want to have more than 2 people in a relationship. There are a number of ways to do this but I would do it like this:
Relationship
------------
ID
StartDate
EndDate
Category
... etc
RelationshipMembers
-------------------
RelationshipID
UserID
Order (may not be needed)
MembershipCategory (eg Professors and Students // messageFrom and messageTo)