In SAP ABAP, mapping two database table fields

I don’t think there is a way to perform this. The common way to do this is by extending original table and fill the new fields.

T-Code: SPDD is somewhat relevant that can be used to compare all the dictionary objects- data elements, tables and structure with old system.

T-Code: SPAU can also be used to compare objects –Reports, Programs, Screens, Messages, Notes, Function Modules etc. which have difference in the Latest SAP request and the previous ones. You can use SPAU just after SPDD or when SAP system upgrade is performed.
Using SPDD and SPAU, you can view all the modified objects, after transporting to the current system. T-code: SPDD contains the list of all modified Data Dictionary objects- tables, data elements, domains, view…etc. The rest of all the modified repository objects will be listed in SPAU.