I am a beginner trying to understand the basic concepts of database's. I know several types of keys (Primary key, Foreign key, candidate key, super key, surrogate key.....etc). While learning about the degenerate dimension, I came across "dimension key".

In a data warehouse, a degenerate dimension is a dimension key in the fact table that does not have its own dimension table ----Ralph Kimball

Could someone please helps me understand the dimension key ?

  • If you are a beginner you should probably leave data warehouse design concepts for now and focus more on normalization forms. Jul 9 '19 at 9:10

A dimension key is the primary key of a dimension table.

In the example below, the "Time_key" column is the dimension/primary key of the Time dimension. This column will be used to join the dimension with fact tables, just like any other key.

Time dimension example

in https://www.kimballgroup.com/1997/07/its-time-for-time/

A degenerate dimension is, however, a different and slightly more advanced concept to model. In the degenerate dim case, a fact table contains a foreign key that, by design, does not link to a dimension.

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