if !NULL ?

On Thu, 16 May 2002, Lev Lvovsky wrote:

ok, so more odd-ball questions

I have two columns in a table:

bool_bill | billing_id

one is a boolean that determines if we bill a customer, and the other one
is NULL if we don't, and has a billing_id of that customer if we do. the
billing_id uses a foreign key on the billing table to check that the
billing_id exists.

what I'd like to do is if bool_bill = y, then there has to be something in
billing_id (automatically checked with the foreign key).

again, do I need a function for this?

I think a table check constraint like:
(bool_bill=false or billing_id is not null)
will make billing_id not accept nulls when bool_bill is true.

Is there a way to do to define a default value when doing this?

something like...

select distinct
uid ....stuff...

e.thingy AS Ifnull(ulk,description,'UNKNOWN'),

... more stuff ...

As I want to do is have a default value of "UNKNOWN" instead of null.

-----Original Message-----
From: Stephan Szabo [mailto:sszabo@megazone23.bigpanda.com]
Sent: Thursday, May 16, 2002 6:17 PM
To: Lev Lvovsky
Cc: pgsql-general@postgresql.org
Subject: Re: [GENERAL] if !NULL ?

On Thu, 16 May 2002, Lev Lvovsky wrote:

ok, so more odd-ball questions

I have two columns in a table:

bool_bill | billing_id

one is a boolean that determines if we bill a customer, and the other one
is NULL if we don't, and has a billing_id of that customer if we do. the
billing_id uses a foreign key on the billing table to check that the
billing_id exists.

what I'd like to do is if bool_bill = y, then there has to be something in
billing_id (automatically checked with the foreign key).

again, do I need a function for this?

I think a table check constraint like:
(bool_bill=false or billing_id is not null)
will make billing_id not accept nulls when bool_bill is true.

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On Fri, 17 May 2002, McCaffity, Ray (Contractor) wrote:

Is there a way to do to define a default value when doing this?

something like...

select distinct
uid ....stuff...

e.thingy AS Ifnull(ulk,description,'UNKNOWN'),

... more stuff ...

As I want to do is have a default value of "UNKNOWN" instead of null.

Well, you can just set a default on the column, although in the
case of foreign keys the default isn't necessarily automatically
allowed unless it's NULL.

Try the COALESCE function

dev=> select version();
version
-------------------------------------------------------------
PostgreSQL 7.2.1 on i686-pc-linux-gnu, compiled by GCC 2.96
(1 row)

dev=> SELECT COALESCE(NULL,'UNKNOWN');
case
---------
UNKNOWN
(1 row)

dev=> SELECT COALESCE('Temp','UNKNOWN');
case
------
Temp
(1 row)

Darren Ferguson

On Fri, 17 May 2002, McCaffity, Ray (Contractor) wrote: