> I believe it's advantageous to avoid nullable columns in relational schema design, but that's a separate issue from the concept of NULL in SQL as distinct fro

> I believe it's advantageous to avoid nullable columns in relational schema design, but that's a separate issue from the concept of NULL in SQL as distinct from programmatic languages. Agreed, but they should be used where appropriate. My favorite example of a nullable column is an end date. Until an end date occurs, it's unknown - thus null. Representing the unknown end date with anything other than null is semantically incorrect, and in many cases can lead to errors.