MSSQL: reusable way of querying subset of all data in a table - sql-server

Question

Suppose a system where People have access to Buildings and in the buildings, have access to certain Rooms.
Access is defined according to the associated Permissions tables or in the case of people with full access, full access.
The db tables are defined as follows:
buildings (id INT)
rooms (id INT, building_id INT)
people (id INT, has_full_access BIT)
building_permissions (building_id INT, person_id INT)
room_permissions (room_id INT, person_id INT)
Currently I have table-valued functions that return tables with the authorised ids of buildings and rooms based on the person's id and whether they have full access.
CREATE FUNCTION fn_get_authorised_buildings (#person_id INT, #has_full_access BIT)
RETURNS TABLE AS
RETURN
(
SELECT b.id
FROM buildings b
WHERE #has_full_access = 1
UNION
SELECT b.id
FROM buildings b
INNER JOIN building_permissions bp ON bp.building_id = b.id
WHERE bp.person_id = #person_id
);
CREATE FUNCTION fn_get_authorised_rooms (#person_id INT, #has_full_access BIT)
RETURNS TABLE AS
RETURN
(
SELECT r.id
FROM rooms r
WHERE #has_full_access = 1
UNION
SELECT r.id
FROM rooms r
INNER JOIN room_permissions rp ON rp.room_id = r.id
WHERE rp.person_id = #person_id
);
Throughout the system whenever buildings and rooms are involved I need to filter those tables based on the person's permissions. If the person has full access then all the rows must be included, otherwise only those that they have permission for.
My queries (simplified) look something like this:
DECLARE #person_id INT = 123
DECLARE #has_full_access BIT = 1
DECLARE #authorised_buildings TABLE (id INT)
INSERT INTO #authorised_buildings SELECT id FROM fn_get_authorised_buildings(#person_id , #has_full_access)
DECLARE #authorised_rooms TABLE (id INT)
INSERT INTO #authorised_rooms SELECT id FROM fn_get_authorised_rooms(#person_id, #has_full_access)
--Example A
SELECT *
FROM buildings b
INNER JOIN rooms r ON r.building_id = b.id
WHERE 1 = 1
AND b.id IN (SELECT id FROM #authorised_buildings)
AND r.id IN (SELECT id FROM #authorised_rooms)
--Example B
SELECT *
FROM floors f -- or other tables that are related to rooms
INNER JOIN rooms r ON r.floor_id = f.id
WHERE 1 = 1
AND r.id IN (SELECT id FROM #authorised_rooms)
Is there a better way to do this?
EDIT:
Here is a fiddle with the setup

Answer 1

You can create a view like this that contains all the logic:
CREATE VIEW bulding_rooms_per_person AS
SELECT p.id AS person_id, b.id as building_id, r.id AS room_id
FROM people p
LEFT JOIN building_permissions bp ON bp.person_id = p.id
LEFT JOIN room_permissions rp ON rp.person_id = p.id
INNER JOIN buildings b ON b.id = bp.building_id OR p.has_full_access = 1
INNER JOIN rooms r ON r.building_id = b.id AND (r.id = rp.room_id OR p.has_full_access = 1)
And then just query over it:
SELECT * from bulding_rooms_per_person WHERE person_id = #person_id