Hi Sathosh,
I'm having a little trouble understanding if you are trying to create a new unique id for the unique combination of the four fields (subtypcd, floor_id_code, floor_id_full_name, asset_id), or if you are trying to create the field ASSET_ID based on the unique combination of the other three.
Can you make it a bit clearer on what data you currently have, and what field you are trying to populate? I'm thinking others might be confused too, and that may be why you haven't received any responses yet.
it would also help to know if this is a feature class in a FGDB or a SQL or Oracle database, or other. It might not matter, but would not hurt to include that info. Also, are you trying to automate this with Python code, Model builder, Field-calculator or a different process.
If you have already tried some code in python or some other method, it would also help if you say what you have tried to give others a starting point. This might prompt more responses.