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From Ryan McFall <mcf...@hope.edu>
Subject Re: Sequences as default values for a column
Date Thu, 14 Jul 2011 11:14:28 GMT
Thanks for the reply, Rick.  I was using identify columns, but then found
that Oracle does not support identity columns, only sequences.  Since I'm
looking for cross-database portability, I'm sticking with sequences - I'm
using Hibernate, and it will automatically choose between a sequence and
using a table to simulate a sequence based on capabilities of the DB.

Ryan

> From: Rick Hillegas <rick.hillegas@oracle.com>
Subject: Re: Sequences as default values for a column
Hi Ryan,

I don't know whether you have considered identity columns. Identity columns
may give you what you need. See the Derby Reference Guide topics " CREATE
TABLE statement" -> "column-definition" -> "generated-column-spec". Right
now, identity columns provide less concurrency than sequences do. However,
identity columns should catch up to sequences in 10.8.2 due to the work on
https://issues.apache.org/jira/browse/DERBY-4437

Hope this helps,
-Rick

On 7/8/11 12:59 PM, Ryan McFall wrote:
>From what I can see in the Derby documentation, it's not possible to
specify the value of a sequence as the default value for a column.  Is my
reading of this correct?

I've seen solutions online for Oracle, which also supports sequences, that
suggest using a before insert trigger to modify the value of a column with a
sequence value if the value is not specified.  This seems like it's more
work than it should be; specifying it as a default in the table definition
makes much more sense to me.

Thanks for any insights you have,
Ryan

-- 
Ryan McFall
Associate Professor of Computer Science
Hope College
Holland, MI  49423
Email: mcfall@hope.edu
Phone: 616-395-7952
Fax: 616-395-7123
http://www.hope.edu/cs/mcfall/

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