From: Thomas F.O'Connell <tfo@sitening.com>
To: Don Drake <dondrake@gmail.com>
Cc: pgsql-sql@postgresql.org
Subject: Re: plpgsql functions and NULLs
Date: Mon, 31 Jan 2005 14:25:03 -0600
Message-ID: <9719e3dd9d6201fc40efcf3a15b82442@sitening.com> (raw)
In-Reply-To: <6c21003b0501301141234c256b@mail.gmail.com>
References: <6c21003b0501301141234c256b@mail.gmail.com>
This sounds like a perfect candidate for a LEFT OUTER JOIN. See:
http://www.postgresql.org/docs/7.4/static/queries-table-
expressions.html#QUERIES-FROM
Yours would looks something like:
SELECT *
FROM ...
LEFT JOIN candidate AS c
ON <...>.omcr_id = c.omcr_id
AND ...
-tfo
--
Thomas F. O'Connell
Co-Founder, Information Architect
Sitening, LLC
http://www.sitening.com/
110 30th Avenue North, Suite 6
Nashville, TN 37203-6320
615-260-0005
On Jan 30, 2005, at 1:41 PM, Don Drake wrote:
> OK, I have a function that finds records that changed in a set of
> tables and attempts to insert them into a data warehouse.
>
> There's a large outer loop of candidate rows and I inspect them to see
> if the values really changed before inserting.
>
> My problem is that when I look to see if the row exists in the
> warehouse already, based on some IDs, it fails when an ID is NULL.
> The ID is nullable, so that's not a problem.
>
> But I'm forced to write an IF statement looking for the potential NULL
> and write 2 queries:
>
> IF omcr_id is null
> select * from ....
> WHERE omcr_id is NULL
> AND ...
> ELSE
> select * from ....
> WHERE omcr_id=candidate.omcr_id
> AND ....
> END IF;
>
> IF FOUND
> ...
>
> Is there a way to do the lookup in one statement?? This could get ugly
> quick. I'm using v7.4.
>
> Thanks.
>
> -Don
>
> --
> Donald Drake
> President
> Drake Consulting
> http://www.drakeconsult.com/
> 312-560-1574
>
> ---------------------------(end of
> broadcast)---------------------------
> TIP 4: Don't 'kill -9' the postmaster
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To: pgsql-sql@postgresql.org
Cc: tfo@sitening.com, dondrake@gmail.com
Subject: Re: plpgsql functions and NULLs
In-Reply-To: <9719e3dd9d6201fc40efcf3a15b82442@sitening.com>
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