[spectre256]

I'm a pilot, and absolutely this is a crucial difference.

It also reminds me of a time years ago when a team I was on had to extend a Memcache client library, as it couldn't differentiate between the following two conditions:

- "I tried to retrieve a key from cache but was unsuccessful (due to connection error, etc)"

- "I tried to retrieve a key from cache but determined conclusively that key does not exist in the cache"

If it was important for a caching layer on our silly social game, the same thing is clearly important in aviation.

[segmondy]

Most people experience the same when using DB, NULL in a database is hard to distinguish from, data never stored or data don't exist.

[kbenson]

Do you mind explaining what you mean? To my knowledge, inspecting the number of rows returned eliminates this problem.