How can I do select case to this query? - sql-server

Question

SQL FIDDLE DEMO HERE
I have this structure of tables:
CREATE TABLE Users
([UserId] int,
[IdDepartment] int);
INSERT INTO Users
([UserId], [IdDepartment])
VALUES
(1, 5),
(2, 0),
(3, -1),
(4, 0),
(5, -1),
(6, 0);
CREATE TABLE Department
([IdDepartment] int, [Name] varchar(23), [IdUser] int);
INSERT INTO Department
([IdDepartment], [Name], [IdUser])
VALUES
(1, 'Sales', 3),
(2, 'Finance', null ),
(3, 'Accounting' , 5),
(4, 'IT' ,3),
(5, 'Secretary',null),
(6, 'Sport',3);
I want to get a query with this results:
In the Users table if the IdDepartment is 0 ist means that the user is an admin so he can see all the departments. If the user has a -1 in the idpartment it means that the user can access to limited departments, so in this case I do a inner join to the Department table to get the list of this departments. The last case is if the user has a number for the idDepartament in the user table diferent to 0 and diferent to -1 it means that the user can access only to this department.
I tried to do something like that, but it is not well structured:
select
case idDepartment
when 0 then (select Name from Department)
when -1 then (select Name from Department where IdUser = 3)
else (select Name from Department
inner join Users on Department.idDepartment = Users.Department
where Users.UserId = 3)
end
from
Department
where
IdUser = 3
How can I do this? thanks.
I add an example for what I want to get:
-For the user that has the userid (1) -->
Department Name
---------------
Secretary
-For the user that has the userid (2) -->
Department Name
---------------
Sales
Finance
Accounting
IT
Secretary
Sport
-For the user that has the userid (3) -->
Department Name
---------------
Sales
IT
Sports

Answer 1

You cant do something like that in a SELECT CASE, the best option is to just introduce some logic
DECLARE #IdUser INT = 3
DECLARE #userDepartment INT
SELECT #userDepartment = IdDepartment
FROM Users
WHERE UserId = #IdUser
IF #userDepartment = 0
BEGIN
SELECT Name FROM Department
END
ELSE IF #userDepartment = -1
BEGIN
SELECT Name FROM Department WHERE IdUser = #IdUser
END
ELSE
BEGIN
SELECT Name FROM Department
INNER JOIN Users
ON Department.idDepartment = Users.IdDepartment
WHERE Users.UserId = #IdUser
END
By the way, You've hit upon why your structure is not ideal. If you had a junction table between Users & Departments, you could model any combination of what you have already with a much simpler query (At the cost of lots of rows in your junction table)

Answer 2

Your sample code is a bit confusing but feels like you are looking for something like this:
declare #id_user int = 3
select d.IdDepartment, d.Name
from Department d
where exists
(
select 1
from Users u
where u.[UserId] = #id_user
and u.IdDepartment in (0, d.IdDepartment)
)
or d.[IdUser] = #id_user
which implements:
if IdUser in Department table is the same as #id_user given - he has access to this department for sure
otherwise this user has access to department if his IdDep value is 0 or equal to corresponding department ID
But your permissions/security model smells not good and it's absolutely not scalable. You'd better invent another entity (table) to store permitted tuples: (IdUser, IdDepartment). Select statements would look much more clear in this case.

Answer 3

declare #IdUser int = 3;
SELECT u.[UserId], d.Name
from Users u
join Department d
on u.[IdDepartment] = 0
or ( u.[IdDepartment] = -1 and d.[IdUser] = u.[UserId] )
or ( u.[IdDepartment] > 0 and d.[IdDepartment] = u.[IdDepartment] )
where u.[UserId] = #IdUser
order by u.[UserId], d.Name
userID 3 should include sport

Answer 4

If I understand from your pseudo-query what you're trying to do, you can do it with a carefully constructed WHERE clause:
case idDepartment
when 0 then (select Name from Department)
when -1 then (select Name from Department where IdUser = 3)
else (select Name from Department inner join Users on Department.idDepartment = Users.Department where Users.UserId = 3)
end
Could be written as a sub-select:
(SELECT Name
FROM Department
LEFT OUTER JOIN Users
on Department.idDepartment = Users.Department
WHERE idDepartment=0
OR (idDepartment = -1 AND idUser = 3)
OR (Users.UserId = 3)
)
You would have to correlate the sub-select to your outer query, of course.