Assign group identifier during ETL? Need suggested approach

Question

Ok, so I need to pull in some data to a "staging" table.  During the process that loads the destination db, I need to assign a value to a field that will be a unique identifier for a group of records that share the same values for a set of
columns.
The overall process looks like kinda like this
Database A -> ETL -> Staging Database B -> ETL -> Database C
I suppose one way to do this is to simply use a calculated column in the statement that selects the data to be loaded into C.  
In  a staging  table in B, there will be records that are related to one another based on a set of columns.  Its this set of column values that I would want to use to generate a "calculated" group identifier in the destination table
in C.
Suggestions?  I suppose my main concern is the generation of the group id, but what to do with those records that couldnt be assigned a group id?

Answer 1

I need to assign a value to a field that will be a unique identifier for a group of records that share the same values
for a set of columns.
Sounds like using DENSE_RANK function to generate unique value for each group of values.
You can also use HASHBYTES function passing the concatenated list of columns and generated byte value corresponding to
them to identify the group of records
see an example here
http://visakhm.blogspot.in/2014/06/ssis-tips-implementing-scd.html
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