From: Erik Jones <erik@myemma.com>
To: Michael Glaesemann <grzm@seespotcode.net>
Cc: Gera Mel Handumon <geramel.h@gmail.com>
Cc: pgsql-sql@postgresql.org
Subject: Re: NULLIF problem
Date: Wed, 28 Nov 2007 13:00:49 -0600
Message-ID: <F0B783FE-5CDA-4B67-99AA-0F0731308D68@myemma.com> (raw)
In-Reply-To: <17DF2022-C1D2-4D9E-ABAC-DC3F5B20FBE7@seespotcode.net>
References: <474404120711271804y21b8e0b3j7f4b3771c088a82a@mail.gmail.com>
<17DF2022-C1D2-4D9E-ABAC-DC3F5B20FBE7@seespotcode.net>
On Nov 27, 2007, at 8:47 PM, Michael Glaesemann wrote:
>
> On Nov 27, 2007, at 21:04 , Gera Mel Handumon wrote:
>
>> I encounter an error if i use NULLIF with timestamp with time zone.
>> eq. dbtime=nullif(mytime,'')
>>
>> i want to null the value of field DBTIME if the variable mytime=" "
>>
>> DBTIME ="timestamp with time zone" datatype
>>
>> error: column DBTIME is of type timestamp with time zone but
>> expression is of type text.
>
> I believe the reason is that '' is not a valid timestamp value:
> think of it this way:
>
> IF mytime = '' THEN
> mytime := NULL;
> END IF;
>
> The first thing it needs to do is compare the mytime value with ''.
> As '' is not a valid timestamp value, it may be casing mytime to
> text. You'll run into problems if you're assigning a text value to
> a timestamp field (which happens after the initial comparison--and
> the cast--are done.)
>
> I think you may need to handle this is you middleware, or handle
> the IF THEN explicitly in a function. Maybe CASE would work:
>
> CASE WHEN mytime = '' THEN NULL
> ELSE CAST(mytime AS TIMESTAMP)
> END
Why not just:
UPDATE table
SET mytime=NULL
WHERE mytime='';
Erik Jones
Software Developer | Emma®
erik@myemma.com
800.595.4401 or 615.292.5888
615.292.0777 (fax)
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To: pgsql-sql@postgresql.org
Cc: erik@myemma.com, grzm@seespotcode.net, geramel.h@gmail.com
Subject: Re: NULLIF problem
In-Reply-To: <F0B783FE-5CDA-4B67-99AA-0F0731308D68@myemma.com>
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