Degenerate dimension is not one that lacks moral structure or integrity. Instead, a degenerate dimension is a dimension that doesn’t exist as a table but is represented in the data warehouse.
Data warehouse dimensional design requires you to include control documents such as invoices, orders, and warranties. Each of these control documents has a control number such as the invoice number, the order number, or the serial number of the item under warranty.
Degenerate dimensions are simply control numbers that are stored in the fact table of a data warehouse. These control numbers look like keys, but they don’t act like keys; they have no associated dimension to join with. Control numbers provide a way to identify which line items in the fact table were generated as a part of the same order or invoice. Let’s take a look at how to map control numbers from the OLTP database to the fact table in the data warehouse and associate them with each line item
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