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In our ongoing series, CEO Michael Olschimke answers a question from the audience regarding Has Key and Hash Diff computation:
“What is the recommended way for Hashing? In the case of an optional relationship, should we first replace the NULL value with the default value before hashing? What is the reason for this? Should we include the BK of parent (hub/link) in calculation of Hash Diff? The above was mentioned in your book ‘Building a scalable Data Warehouse with Data Vault 2.0’ but other blogs emphasize a loading code for a satellite that compares the latest Hash Diff per Hash Key (even if BK is included in Hash Diff). Is there a specific reason?”
Specifically, the discussion delves into whether it is advisable to replace NULL values with default values before hashing in the context of an optional relationship. The rationale behind this practice and the potential inclusion of the BK of the parent (hub/link) in the calculation of Hash Diff are explored.
This topic was previously highlighted in Michael’s book ‘Building a scalable Data Warehouse with Data Vault 2.0’, but contrasting perspectives from other blogs advocate for a loading code approach for a satellite that considers the latest Hash Diff per Hash Key, even if the BK is included in the Hash Diff.
Michael sheds light on the significance of Hash Key and Hash Diff in this discussion.
Meet the Speaker
Michael Olschimke
Michael has more than 15 years of experience in Information Technology. During the last eight years he has specialized in Business Intelligence topics such as OLAP, Dimensional Modelling, and Data Mining. Challenge him with your questions!
