Right, Date's idea didn't catch on. I'm not aware of any industry-strength RDBMS prohibiting storing null. Agreed that queries would tend be longer as you'd ne

Right, Date's idea didn't catch on. I'm not aware of any industry-strength RDBMS prohibiting storing null. Agreed that queries would tend be longer as you'd need joins, although views could help, especially for read operations. Regarding storage-efficiency and query speed, agreed that it could well hurt both, but it's going to depend. If a column holds null in almost all rows, we would expect it to be more space-efficient to use a separate table and a left outer join. Query speed could also improve for queries that don't reference the nullable column, as the 'main' table would be smaller in storage. (I'm assuming a rowstore here.)