Assigning Unique Sequence Numbers Across Different Tables

I have a procedure which updates a sequence number in a table such as the one below.


Seq Sequence_Id

------ ------------------
NextNum 1


This is the procedure ...

create procedure DBO.MIG_SYS_NEXTVAL(@sequence varchar(10), @sequence_id int)
as
begin

update mig_sys_sequences
set
@sequence_id = sequence_id = sequence_id + 1
where
seq = 'CSN'

return(@sequence_id)
end


The purpose of this is to generate a sequential number each time the procedure is called. This number would then be used in a number of different tables to allocate a unique id so that the id is unique across the different tables.


1). What is the most efficient way of allocating these unique ids? The tables that I plan to update will already be populated with data.

2). How would I call the above procedure from an UPDATE statement?

Many thanks,

Fred