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SCD's are nothing but Slowly changing dimension.

Scd's are the dimensions that have the data that changes slowly. Rather than

changing in a time period. That is a regular schedule.

The Scd's are performed mainly into three types.

They are

Type-1 SCD

Type-2 SCD

Type-3 SCD




Type -1 SCD: In the type -1 SCD methodology, it will overwrites the older data

( Records ) with the new data ( Records) and therefore it will not maintain the

historical information.

This will used for the correcting the spellings of names, and for small updates of

customers.


TYpe -2 SCD: In the Type-2 SCS methodology, it will tracks the complete historical

information by creating the multilple records for the given natural key ( Primary

key) in the dimension tables with a separate surrogate keys or a different

version numbers. We have a unlimited historical data preservation, as a new

record is inserted each time a change is made.


Here we use differet type of options inorder to track the historical data of

customers like

a) Active flag

b) Date functions

c) Version Numbers

d) Surrogate Keys


We use this to track all the historical data of the customer.

According to our input, we use required function to track.




Type-3 SCD: In the Type-2 SCD, it will maintain the partial historical

information.








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