On Wed, Jan 15, 2003 at 17:23:09 -0000, dev@archonet.com wrote:
>
> How do nulls work?
> ==================
> There is one very important rule when dealing with nulls. The result of
> any operation or comparison, when applied to a null is null. The only
> exception is testing if a value is null.
I suggest rephrasing this to make it clear you need to use is null to
do this and that = null won't do what you expect.
> If you try to perform an operation on nulls, again the result is always
> null. So the results of all of the following are null:
The above isn't true (i.e. null op something isn't ALWAYS null). For example:
bruno=> select 't'::boolean or null;?column?
----------t
(1 row)