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This is null trivia, a lot of it is not worth memorizing because it's not important. Personally I was surprised that NULL AND FALSE does not result in NULL, but who cares?


> a lot of it is not worth memorizing because it's not important.

Until it is.

If you're not familiar with how NULLs are compared, at least in mysql, it will bite you right in the rectum when you start setting up things like unique constraints on nullable columns.


It is not worth memorizing because it is implementation-dependent.

In Sybase derivatives (hello SQL Server), null can exist once in a unique index. A second insertion fails.

In Oracle, null is not indexed. In composite indexes, they are counted, but do not matter.

My score was 11/22. I guess that I vaguely know what I'm doing.




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