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;
}
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