share datas between 4 websites

I'm planing a webproject, containing 4 websites build in MVC3. As a databaseserver I'm going to use the ms sql server.

Each of this websites will have something arround 40 tables. But some of the tables are shared between the websites: Contact, Cities, Postalcodes, Countries...

How to handle this? should I put all the tables of each database into a common database (so that the database of website 1,2,3 and website 4 are in one databse to开发者_如何学编程gether). Or should I create one database containing shared datase?

But then I think I'm getting problems with the data consitency, because I think there is no way to point from one database to an other (linking for example the citytable in database one to the buldingtable in databse 2).

Any ideas? Thanks a lot!

What I like about splitting it out into separate databases is that if each web site has its own database, and one of those web sites gets extremely popular, it is very easy to just move their database to a different, more powerful database server and not much has to change except (a) you need to reference the central "control" data remotely (or replicate/mirror/etc), and (b) you point that web site at a different database server. Another benefit is that if two web sites have the same types of tables (e.g. Patients), you don't have to have tables like Patients_WebSite1, Patients_WebSite2, with different stored procedures that are identical except for table names (or ugly dynamic SQL procedures that paste the table name in). Separated out you can have the exact same schema and the exact same codebase without having to combine everyone's data into a single table.

If you mix the data within a single database, data consistency is easier, and the whole setup is slightly simpler, but splitting it out when you grow is a lot tougher. If you split it out into different databases, no you won't be able to enforce referential integrity using standard DRI (foreign keys). You can accomplish this in other ways if it is important (triggers, validation before insert/update, etc).