3 ms·

How is that different than “anything”? If I’m comparing a value of type date to a null I still think it works as it should if value is “unknown”. What greater

• mulmen 2y ago
  > How is that different than “anything”? Because the possible values are known. > What greater insight or context do we have if it’s a small-int null? The insight is that null is not a value. It’s not a smallint or a boolean or a date. It’s the absence of a possible value. The only way to see a null as tri-state is to conflate it with a nullable boolean. This is an incorrect mental model which leads to confusion.
• rawgabbit 2y ago
  Suppose you have table with two columns to represent a classroom’s exam scores. It has the columns student_id (varchar) and score (int). If a student is sick and has not taken the exam, yes you could enter -99 to represent they did not take the test. But if you want to find the class average, you would have to do something like this: select average(case when score =-99 then null else score end) as class_avg from … Or you could have entered null to begin with.