how to use multiple database for a single web application?

i am planning to develop a web application that is accessible from the internet.
i want to have a web based application for apartment rent management system.
so the application will register each apartment and the tenants within the apartment.
let say Apartment Abc has 12 floors and 20 rooms on each floor.
then the apartment ABC will be registered in the system along with its tenants,rooms, floors
Apartment xyz has 8 floors and 15 rooms on each floor. xyx's rooms,floors, tenant details will be registered.
apartment def has 5 floors and 20 rooms on each floor, def's rooms,floors,tenant details will be registered on the system.

each apartment will have its own login system, so that when apartment ABC logged in..only his own apartment details will manage(floors,rooms,tenants,payments...)
then number of apartment could be any number...
so how to handle this kind of application, if i should use a single database for each new company(apartment) how can i do that? or if there is a mechansim to handle this kind of application with single database.. let me know please?

If you do a Google search on:

vb .net apartment rent management system

You will get a quite a few hits. Maybe you could get some ideas from those projects.

I didn't download this one but it is advertised as free:

http://1000projects.org/apartment-ma...nt-system.html

Wrong design... you should have one database. For everything...

What if someone has two buildings to manage?

I'd have an Owner/Manager table... then an ApartmentBuilding table with an OwnerID that is an FKey to Owner.... then you could have a Units table that has a BuildingID that is an FKay to the ApartmentBuilding table, then another table that is Tenants with a UnitID that is an FKey to Units table....

When someone logs in, you find their Buildings... give them a list, which one do they want to work with? Then when they select that, give them a list of the units, details, etc....


-tg