What data type is recommended for ID columns?

Question

I realize this question is very likely to have been asked before, but I\'ve searched around a little among questions on StackOverflow, and I didn\'t really find an answer to

Answer 1

If the database is distributed, where you could get records from other databases, the primary key needs to be unique within a table across all the databases. GUID solves this issue, albeit at the cost of space. A combination of autoincrement and namespace would be a good tradeoff.

It would be nice if databases could provide inbuild support for autoincrements with "prefixes". So in one database, I get IDs like X1,X2,X3 ... and so on whereas in the other database it could be Y1,Y2,Y3 ... and so on.