Re: Max date

[Charles Wilt <charles.wilt@xxxxxxxxx>]

I blame Oracle...
https://stackoverflow.com/questions/203493/why-does-oracle-9i-treat-an-empty-string-as-null

Not that I'm against NULLs...I'm very much for them.  But they need to be
used carefully and only where they make sense.

For instance, in the OP's case, for an expiration date, I'd wouldn't use
them.  I'd just set the date to 9999-12-31.  I don't really need a contract
that doesn't expire.  Having it expire when time does is good enough. ;)

In the case of most character fields, you don't usually really need to
differentiate between UNKNOWN and BLANK/EMPTY.

The one place NULLs really come in handy, is numeric fields that you intend
to use aggregate functions on.  AVG(2,2,NULL,2) is 6 / 3=2 not 6 / 4 = 1.5.

Of course, that assumes you want 2 as a result and not 1.5. :)

I think many developers overuse NULL, as DBMS' default to NULLABLE.

Charles

On Wed, Sep 23, 2015 at 6:12 PM, Vernon Hamberg <vhamberg@xxxxxxxxxxxxxxx>
wrote:

> Just to throw something into the fray that is really a non-winning
> attempt, but I'll do it anyway!
>
> NULL - it is not really a value, it is an attribute. That's why the null
> indicators make some sense - it's either true or false that the value of
> something is known. Not that this makes things easy.
>
> When columns are nullable, the row in storage has a bit array (I think -
> maybe a byte array) up to 8000 long - the maximum number of columns in a
> record.
>
> There is no test in SQL for FIELD = NULL - the test is FIELD IS NULL.
>
> The COALESCE function is always described as "...returning the 1st
> non-null expression among it's arguments..." I suggest that "non" is a test
> for "is", not "equals".
>
> I really do think that if we remember this distinction, that things can be
> a little less confusing. As Charles says, you can't say a comparison is
> true or false when a column could BE NULL in some rows.
>
> The trouble with this position is, even IBM in its documentation talks
> about a column having the NULL value - I think! Even people in this list
> find this to be common usage.
>
> Anyhow, there I sit - ready to to be knocked off my NULL position on the
> fence into either the TRUE or FALSE side - hope it's greener, wherever I
> land!