Because the concept is so important in database science, many RDBMS systems implement some type of generated key, although each has its own terminology.
An identity column differs from a primary key in that its values are managed by the server and usually cannot be modified.
In Microsoft SQL Server you have options for both the seed (starting value) and the increment.
By default the seed and increment are both 1. or In PostgreSQL It is often useful or necessary to know what identity value was generated by an INSERT command.
Microsoft SQL Server provides several functions to do this: @@IDENTITY provides the last value generated on the current connection in the current scope, while IDENT_CURRENT(tablename) provides the last value generated, regardless of the connection or scope it was created on.