A Degenerate Dimension is a Dimension which is derived out of a Fact Table and it appears to the end user as a separate/distinct Dimension, its data is actually stored in the Fact Table. It's a Dimension table which does not have an underlying physical table of its own.
Degenerate Dimensions are commonly used when the Fact Table contains/represents Transactional data like Order Details, etc. and each Order has an Order Number associated with it, which forms the unique value in the Degenerate Dimension.
Example:-
Degenerate Dimensions having unique Order Numbers can be used to identify the various items sold as part of a particular order.
Here are some highlights of Degenerate Dimension:
It is derived from the Fact Table and does not have an underlying physical Dimension Table of its own.
It is also called as a Fact Dimension.
Since these dimensions are built on top of Fact Table, these are usually very large dimensions.
The attribute of a Degenerate Dimension is not a Foreign Key in the Fact Table.
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