[dataflow]

> SQL NULLs are not weird once you consider how you want relational logic to work when they is a record with non-existent values.

Could you explain how this makes sense then?

  SELECT ...
  WHERE NULL

If NULL is just "unknown" then shouldn't this be a type error?

Moreover, could you explain why the heck this ought to be empty?

  WITH T AS (SELECT 1 AS C1,
             NULL AS C2)
    SELECT C1, C2
    FROM T
    INNER JOIN T
    USING (C1, C2);

As a human this looks insane to me, "relational algebra" be damned. You find a row, then you look it up again, and it's not there? What the hell?