What are slowly changing dimensions?
Answer Posted / chaitanya
SCD, is a technique used to store the historical value of
dimension attributes.
The values of dimensional attributes change as time goes by.
When these attribute values change, you can overwrite the
old values with the new ones, or you can
preserve the old value.
There are two methods of preserving the old attribute
values: you can store the old values as rows, or you can
store them as columns
three types of SCD:
• SCD type 1 overwrites the old values of the attributes so
the old values are not kept.
Ex: In product dimension,we will use SCD type 1, meaning we
will overwrite the old attribute values.
SCD type 2 keeps the old values by creating a new row for
each change.
SCD type 3 keeps the old values by putting them in another
column
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