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, 2019 at 9:10

1 Answer 1


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.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.