I agree with you about using nonstandard extensions. I'll try to
avoid them in any code I write that may become part of OpenACS.
I think "nothing" vs "unknown" is just semantics, so long as it's
understood that NULL != 0 and NULL != ''. While returning
NULL if one side of an operator is NULL is logical for most
operators, I can certainly see the use of having a string
concatenation operator (in addition to, not instead of, the one we
have now) that treats NULL as empty string.
That being said, perhaps a better solution would be to change the
database schema in some places so that certain fields default to ''
instead of NULL or to make sure the '' is there in the INSERT
statement.
