Re: postgresql vs mysql

>>>If you don't know something, why are you trying to record it? From a strict relational sense, the existence of NULL values in your fields indicates that your primary keys are not
truly candidate keys for all your fields. That means your database isn't [BCNF] normalized.<<<

I agree that there are very few times when NULL is appropriate in a database. I can't think of a single concrete example to use it in a database field.

It has its use in programming, mainly as a memory management/trash collection mechanism. Basically, you don't want to delete something that doesn't exist.

For example:

Statement *st = NULL;
ResultSet *rs = NULL;
try
{
st = prepareStatement("select * from customers");
rs = st->executeQuery();
while (rs->next())
{
do something
}
delete st;
delete rs;
}
catch (Exception e)
{
if (st != NULL)
delete st;
if (rs != NULL)
delete rs;
}