table comparison for fact table? never ever, table comparison is effective, but not that much. What if you FT consist of 1 billion or more rows? Your DBA will not be happy, if you compare data based on index column, then yes, you can achieve good results. Best option how to implement delta load for fact table is to fix the timestamp of fact table and load anly those where Timestamp is greater than one fixed in fact table.
So.
1. Create a Local variable in script and find the Max timestamp value (there should be one)... select max(timestamp_col) from MyFDacttable
2. Then create DF which extracts data from Source system to target and add this vavariable to WHERE tab of Query.
By implementing this you will extract only those values where timestamp is greater than existing one... You can implement the same for multiple columns