What is the junk dimension?

It is common in data warehouse design to run into yes/no indicator fields in source systems. Such information is rather crucial.

In other words, if we keep all those indicator fields in the fact table, we need to create many dimension tables as well as store a tremendous amount of information, resulting in performance and management issues.

The junk dimension is the solution to this problem. We combine these indicator fields into a junk dimension. Thus, we only need to build one dimension table, and the size and number of fields in the fact table can be reduced.