February 2019
Beginner to intermediate
544 pages
14h 36m
English
Content preview from Mastering Hadoop 3
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Slowly changing dimensions – type 1
Slowly changing dimensions type 1 implementation overwrites all the old data with new and updated records. It does not maintain history of old data, meaning we will not be able to track the changes if we want to at some later stage. The approach for the solution is very simple, and the following diagram is a simple representation of SCD type-1:
In programming terms, if we have to solve this problem, there are two approaches, with the database supporting a merge statement, it is easy to run the update and insert in single run using the following sample query:
merge into targetTableusing incoming_table as ...
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