On fös, 2008-11-28 at 15:22 +0100, Lutz Steinborn wrote: > Hello Paul, > > thanks for the quick answer. > > > NULL values? > Jepp, thats it. > I've supposed this but can't believe it. So NULL is something out of this > dimension :-)
Yes, that is one way of putting it. A more useful way to look at it is to say that NULL represents an UNKNOWN value. rows with NULL bar value will not be counted by: > > select count(*) from foo where bar = 'Mr Spock'; because you cannot know whether the UNKNOWN value is 'Mr Spock'. these rows will neither be counted by: > > select count(*) from foo where NOT bar = 'Mr Spock'; because you also cannot know that the UNKNOWN value is NOT 'Mr Spock'. Does that make it any clearer? gnari -- Sent via pgsql-sql mailing list (pgsql-sql@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-sql
