Subject: Re: NOT NULL CHECK (mycol !='') :good idea? bad idea?
To: David W Noon <david.w.noon@googlemail.com>, pgsql-sql@postgresql.org
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 <5751D2C5.3080303@googlemail.com>
From: Adrian Klaver <adrian.klaver@aklaver.com>
Message-ID: <aeb5d614-c77e-073c-e25a-4eb1dbfc3b7a@aklaver.com>
Date: Fri, 3 Jun 2016 12:05:58 -0700
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On 06/03/2016 11:56 AM, David W Noon wrote:
> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA1
>
> On Fri, 3 Jun 2016 11:16:33 -0700, Michael Moore
> (michaeljmoore@gmail.com) wrote about "[SQL] NOT NULL CHECK (mycol
> !='') :good idea? bad idea?" (in
> <CACpWLjPX-_80aXcJFbk7wxZWKPTs2Fyeywe=6HmgorzV2U=n7A@mail.gmail.com>):
>
>> In Oracle, a NOT NULL constraint on a table column of VARCHAR in
>> essence says: "You need to put at least 1 character for a value".
>> There is no such thing as a zero-length string in Oracle, it's
>> either NULL or it has some characters.
>
> So Oracle is not compliant with ANSI standard SQL.

Though it looks like they want to be:

http://docs.oracle.com/database/121/SQLRF/sql_elements005.htm#SQLRF30037

"Note:
Oracle Database currently treats a character value with a length of zero 
as null. However, this may not continue to be true in future releases, 
and Oracle recommends that you do not treat empty strings the same as 
nulls."


-- 
Adrian Klaver
adrian.klaver@aklaver.com


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