ALTER TABLE

In earlier versions, you can use later statement for tables, specifying four part table names. For example specifying the format .database.schema.table or the format ..schema.table will be succeeded. However, in SQL Server 2012 it will fail.

So in case you have referenced tables when altering them as a four part table name, make sure you change them. You might not use this type of statements directly however there are chances that applications, will use for ad-hoc queries.