Question

I have a table called Request and data will be entered by two types of users (Company staff and site members). Initially I had a column called createdby. But, the staff and the members table primary keys are integers with identity. So i had to change it because there could be an ID that corresponds to both entities.

Then I have created two columns in the the request table ByStaffId and ByMemberID. I wonder whether it is the right way.

Answer 1

Below is an example of how to relate the Staff and Members together using a common User table that has a 1-to-1 relationship with both a StaffUser table and a MemberUser table.

Granted, this approach results in greater complexity when selecting/inserting/updating/deleting users, so you can decide whether this is worth the extra complexity.

create table [User]
(
    UserID int identity(1,1) not null primary key,
    Username nvarchar(50) not null
)

create table StaffUser
(
    UserID int not null primary key references [User] (UserID),
    FirstName nvarchar(50) not null,
    LastName nvarchar(50) not null
)

create table MemberUser
(
    UserID int not null primary key references [User] (UserID),
    Email nvarchar(100) not null,
)

create table Request
(
    ByUserID int not null references [User] (UserID),
)

declare @UserID int

insert into [User] values ('john.smith')
set @UserID = scope_identity()
insert into StaffUser values (@UserID, 'John', 'Smith')

insert into Request values (@UserID)

insert into [User] values ('billy.bob')
set @UserID = scope_identity()
insert into StaffUser values (@UserID, 'Billy', 'Bob')

insert into Request values (@UserID)

insert into [User] values ('member1')
set @UserID = scope_identity()
insert into MemberUser values (@UserID, '[e-mail]')

insert into Request values (@UserID)

insert into [User] values ('member2')
set @UserID = scope_identity()
insert into MemberUser values (@UserID, '[e-mail]')

insert into Request values (@UserID)

insert into [User] values ('member3')
set @UserID = scope_identity()
insert into MemberUser values (@UserID, '[e-mail]')

insert into Request values (@UserID)

-- select staff
select
    StaffUser.UserID,
    [User].Username,
    StaffUser.FirstName,
    StaffUser.LastName
from StaffUser
inner join [User] on
    [User].UserID = StaffUser.UserID

-- select members
select
    MemberUser.UserID,
    [User].Username,
    MemberUser.Email
from MemberUser
inner join [User] on
    [User].UserID = MemberUser.UserID


-- select all users
select
    StaffUser.UserID,
    [User].Username
from StaffUser
inner join [User] on
    [User].UserID = StaffUser.UserID

union all

select
    MemberUser.UserID,
    [User].Username
from MemberUser
inner join [User] on
    [User].UserID = MemberUser.UserID


select * from Request


drop table Request
drop table MemberUser
drop table StaffUser
drop table [User]

---

Below is a slightly more complicated structure that accomplishes the same thing as the example above, but in this case Member and Staff are more decoupled from User.

create table [User]
(
    UserID int identity(1,1) not null primary key,
    CreatedOn datetime not null default getdate()
)

create table StaffUser
(
    UserID int not null primary key references [User] (UserID)
)

create table MemberUser
(
    UserID int not null primary key references [User] (UserID)
)

create table Staff
(
    StaffID int identity(1,1) not null primary key,
    FirstName nvarchar(50) not null,
    LastName nvarchar(50) not null,
    UserID int null references StaffUser (UserID),
)

create table Member
(
    MemberID int identity(1,1) not null primary key,
    Username nvarchar(50),
    Email nvarchar(100) not null,
    UserID int null references MemberUser (UserID),
)

create table Request
(
    ByUserID int not null references [User] (UserID),
)

declare @UserID int

insert into [User] default values
set @UserID = scope_identity()
insert into StaffUser values (@UserID)
insert into Staff values ('John', 'Smith', @UserID)

insert into Request values (@UserID)

insert into [User] default values
set @UserID = scope_identity()
insert into StaffUser values (@UserID)
insert into Staff values('Billy', 'Bob', @UserID)

insert into Request values (@UserID)

insert into [User] default values
set @UserID = scope_identity()
insert into MemberUser values (@UserID)
insert into Member values ('member1', '[e-mail]', @UserID)

insert into Request values (@UserID)

insert into [User] default values
set @UserID = scope_identity()
insert into MemberUser values (@UserID)
insert into Member values ('member2', '[e-mail]', @UserID)

insert into Request values (@UserID)

insert into [User] default values
set @UserID = scope_identity()
insert into MemberUser values (@UserID)
insert into Member values ('member3', '[e-mail]', @UserID)

insert into Request values (@UserID)

-- select staff
select
    Staff.StaffID,
    Staff.FirstName,
    Staff.LastName,
    Staff.UserID
from Staff

-- select members
select
    Member.MemberID,
    Member.Username,
    Member.Email,
    Member.UserID
from Member

-- select all users
select
    [User].UserID,
    Staff.FirstName + ' ' + Staff.LastName as Name,
    [User].CreatedOn
from [User]
inner join Staff on
    Staff.UserID = [User].UserID

union all

select
    [User].UserID,
    Member.Username as Name,
    [User].CreatedOn
from [User]
inner join Member on
    Member.UserID = [User].UserID


select * from Request


drop table Request
drop table Member
drop table Staff
drop table MemberUser
drop table StaffUser
drop table [User]