Which is SCD type 2. What is its behavior?

SCD type 2 is a Slowly Changing Dimension strategy that preserves the full history of changes to a dimension record. When a change occurs, instead of overwriting the existing row, a new row is inserted with a new surrogate key, an effective start date, an end date (often set to a future date or NULL for the current record), and a flag indicating whether the row is current. This allows queries to retrieve both the current state and the historical state of a dimension. For example, if a customer’s address changes, the old address row remains in the fact table with its original dates, while a new row with the updated address is added. This behavior is essential for time‑based reporting and auditing.