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From "Dyre Tjeldvoll (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (DERBY-6340) Add support for CREATE TYPE AS <existing type> (synonym types)
Date Mon, 07 Oct 2013 09:51:42 GMT

    [ https://issues.apache.org/jira/browse/DERBY-6340?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13788025#comment-13788025

Dyre Tjeldvoll commented on DERBY-6340:

Hi Rick, thank you for your comments. 

I agree that the std does not mention comparison of distinct types to their STs, so that a
cast is required in this case. I have updated the fs accordingly. I have also added a description
of the the default identifiers for the casting functions. 

When it comes to the namespace of distinct UDT, I wondered if you could clear up a few things:

My understanding of Part 2, section 11.51 (user-defined type definition), general rule 2.b,
is that the casting functions are created in the explicit or implied schema of the UDT. "CREATE
FUNCTION SN.FNUDT ( ... where: SN is the explicit or implicit <schema name> of UDTN".
Is DERBY-5901 the reason why the name must not conflict with a builtin function or aggregate?

A couple of observations:

* Without the ability to specify <cast to source> you can create at most one alias for
each builtin type in the same schema?
* Due to DERBY-5901, we must either always specify <cast to source> or let the default
identifier be non-standard as the default names mandated by the standard are already used
by existing builtin functions in Derby?

Do you agree?

> Add support for CREATE TYPE AS <existing type> (synonym types)
> --------------------------------------------------------------
>                 Key: DERBY-6340
>                 URL: https://issues.apache.org/jira/browse/DERBY-6340
>             Project: Derby
>          Issue Type: Improvement
>          Components: SQL
>            Reporter: Dyre Tjeldvoll
>            Assignee: Dyre Tjeldvoll
>         Attachments: CreateTypeAs_fs_draft_2.html, CreateTypeAs_fs_draft.html
> The SQL standard (2003) chapter 11.41 <user-defined type definition> allows the
creation of synonyms or aliases for an existing type: CREATE TYPE AS <predefined type>.
By allowing this in Derby we would simplify migration from, and interoperation with, other

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