Re: 3vl 2vl and NULL

On 4 Dec 2005 17:57:01 -0800, michael_at_preece.net wrote:

(snip)
>OK. There is one fundamental problem with this. Some of those NULLs in
>those tuples might represent that we know something is empty - so it
>has to be treated as a known value. All NULLs are not created equal.

<sigh>

Hi Mike,

No. If something is known to be empty, it's not stored as NULL. At least not in SQL databases (which this thread is about, IIRC).

If a comment is empty, iut's stored as the empty string (''). If a container is empty, it's contents is stored as zero gallons (0). Dates can't be empty. (Days can be, though - that's stored as an absence of rows in the Events table).

Best, Hugo

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