logoalt Hacker News

mrkeen • yesterday at 7:59 PM • 2 replies • view on HN

I won't push back on it being garbage, but I would suggest that if enough people did it that way it would be the new normal, and apologists would fall out of the woodwork, e.g. [1]

I complain that mainstream SQL engines have no problem returning less than the total number of rows if you first query WHERE column = NULL and then query WHERE column <> NULL. Your example queries remind me of that.

[1] https://medium.com/dailyjs/the-why-behind-the-wat-an-explana...

Replies

semiquaver • yesterday at 8:10 PM

  > WHERE column = NULL and then query WHERE column <> NULL
With respect, your statement seems to indicate that you simply haven’t heard of or don’t understand the three-valued-logic semantics behind SQL.

NULL means what it means and is conceptually foundational to SQL. Comparing it to anything returns UNKNOWN, the “third value” besides true and false. And WHERE needs a TRUE predicate. So your implied fault that they “have no problem“ really is just a matter of you not understanding the tool you are complaining about.

To match against the NULLness of a value you must use special purpose operators. In this case

   WHERE column IS NULL OR column IS NOT NULL
➕ show 1 reply
CodesInChaos • yesterday at 8:28 PM

I am rather receptive to the argument that SQL is a fractal of bad design. But complaining that SQL engines implement well known SQL semantics according to spec is silly.