Postgres Pro
Downloads
Home   >   mailing lists

Thread: NULL OR ZERO

NULL OR ZERO

From
"Omar Bettin"
Date:
Probably I am on the wrong place but for me NULL on numbers means 0 or ZERO.
I know about standards...

but I think that integralism is somewhat wrong.
Omar
a programmer...

Re: NULL OR ZERO

From
"Jaime Casanova"
Date:
On Feb 3, 2008 7:26 PM, Omar Bettin <o.bettin@tiscali.it> wrote:
> Probably I am on the wrong place but for me NULL on numbers means 0 or ZERO.
> I know about standards...
>

NULL means unknown value, ZERO is a known value

-- 
regards,
Jaime Casanova

"Programming today is a race between software engineers striving to
build bigger and better idiot-proof programs and the universe trying
to produce bigger and better idiots.
So far, the universe is winning."                                      Richard Cook

Re: NULL OR ZERO

From
Andrei Kovalevski
Date:
Hello,

Omar Bettin wrote:
> Probably I am on the wrong place but for me NULL on numbers means 0 or 
> ZERO.
> I know about standards...
>

You can easily convert NULLs to 0 in your queries - read about COALESCE 
function 
http://www.postgresql.org/docs/8.0/interactive/functions-conditional.html. 
Compare these SELECTs:

CREATE TABLE test (num INTEGER);
INSERT INTO test VALUES (1), (2), (null), (3), (null), (4), (0);

SELECT num FROM test;

SELECT COALESCE(num, 0) FROM test;


> but I think that integralism is somewhat wrong.
>
> Omar
> a programmer...
>
> ---------------------------(end of broadcast)---------------------------
> TIP 9: In versions below 8.0, the planner will ignore your desire to
>       choose an index scan if your joining column's datatypes do not
>       match


-- 
Andrei Kovalevski
PostgreSQL Replication, Consulting, Custom Development, 24x7 support
Managed Services, Shared and Dedicated Hosting
Co-Authors: plPHP, ODBCng - http://www.commandprompt.com/

Re: NULL OR ZERO

From
"Rodrigo E. De León Plicet"
Date:
On Feb 3, 2008 7:41 PM, Jaime Casanova <systemguards@gmail.com> wrote:
> On Feb 3, 2008 7:26 PM, Omar Bettin <o.bettin@tiscali.it> wrote:
> > Probably I am on the wrong place but for me NULL on numbers means 0 or ZERO.
> > I know about standards...
> >
>
> NULL means unknown value, ZERO is a known value

NULL represents absence of a value. You get the UNKNOWN truth value if
you compare NULL with any data value or another NULL (damn you, 3VL!).