In data warehouse-ing, a junk dimension is used to manage and consolidate various low-cardinality attributes that do not fit neatly into the main dimensions.
These attributes, often flags or indicators such as “yes/no” values, statuses, or other small categorical data, are combined into a single junk dimension table.
This approach helps to simplify the database schema by avoiding the proliferation of multiple small dimension tables and reducing the number of foreign keys in the fact table. By grouping these attributes together, the junk dimension improves data organization and query performance while maintaining a clean and efficient star schema design. It also facilitates easier maintenance and enhances the readability of the data model.