189 ) How do you deal with duplicate records into your Fact table?

 How do you deal with duplicate records coming from the source Oracle or SQL Server systems into your Fact table?

Answer:

We prevent duplicates at multiple stages:

1. Staging Checks: In our staging area, we write deduplication logic using window functions (like ROW_NUMBER()) to drop exact duplicate rows before they hit the warehouse.
2. Unique Business Keys: In our fact tables, we define natural keys or composite unique constraints (such as combining Policy_ID, Transaction_Date, and Transaction_Type) so that if the same daily file is accidentally loaded twice, the load fails or skips the duplicates.