SQL: Using NULL values vs. default values

Question

What are the pros and cons of using NULL values in SQL as opposed to default values?

Answer 1

In a Data Warehouse, you would always want to have default values rather than NULLs.

Instead you would have value such as "unknown","not ready","missing"

This allows INNER JOINs to be performed efficiently on the Fact and Dimension tables as 'everything always has a value'