Re: So what's null then if it's not nothing?
Date: 10 Dec 2005 18:12:26 -0800
Message-ID: <1134267146.767667.96760_at_g43g2000cwa.googlegroups.com>
Hello, I have 1 question about the 3VL that hopefully someone can
answer. With data that we cannot avoid is missing we may have a
true/false column that can have nulls in it which gives us a 3VL so
that:
((column_1=T) && (column_2=T)) = T
Now, I read in the thread that for this to be a sensible logic we have
?=?. Ok, but that means that an unknown equals another unknown. That
does not seem to make sense because by saying ? we at the start said
((column_1=T) && (column_2=F)) = F
((column_1=F) && (column_2=F)) = F
((column_1=T) && (column_2=?)) = ?
((column_1=F) && (column_2=?)) = ?
((column_1=?) && (column_2=?)) = ?