A Slowly Changing Dimension (SCD) is a dimension that stores and manages both current and historical data over time in a data warehouse. It is considered and implemented as one of the most critical ETL tasks in tracking the history of dimension records.A Type 2 SCD retains the full history of values. When the value of a chosen attribute changes, the current record is closed. A new record is created with the changed data values and this new record becomes the current record. Each record contains the effective date and expiration date to identify the time period between which the record was active.In this Type 2 SCD, the old values will not be replaced, but a new row containing the new values will be added to the customer table. So at any point of time, the difference between the old values and new values can be retrieved and easily be compared. This would be very useful for reporting.

Cust_Key	Cust_No	Name	City	State	Country	Phone_No	Start_Date	End_Date
01	1001	John	NewYork	NY	USA	8312222222	01-JAN-1990	31-DEC-9999
02	1002	Micheal	NewYork	NY	USA	9848022338	01-JAN-1990	14-MAR-2014
03	1002	Micheal	Greensboro	NC	USA	9848022338	15-Mar-2014	31-DEC-9999