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Comment by wireprotocol | Hacker News Reader

"Empty set differs from NULL is that you get an empty set if you apply an element-wise function over it"

It still sounds like NULL -- I must be missing something.

Take the CASE WHEN example from the blog. An equivalent EdgeQL expression is

  SELECT 'one' IF value = 1 ELSE 'not one'

If value is an empty set, then the result is _always_ an empty set, unlike SQL that pretends NULL values are actually boolean for the purposes of the condition. EdgeQL expressions are, essentially, set comprehensions, the above is equivalent to this Python expression:

  {'one' if v = 1 else 'not one' for v in value}

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