How to create database level counter (identify field)?
Sounds like Sequences, brought in with SQL 2012

Info:
https://msdn.microsoft.com/en-us/library/ff878058.aspx
Create Sequence syntax:
https://msdn.microsoft.com/en-us/library/ff878091.aspx
Nice SimpleTalk article on them:
https://www.simple-talk.com/sql/learn-sql-server/sql-server-sequence-basics/