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From "Rick Hillegas (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (DERBY-6340) Add support for CREATE TYPE AS <existing type> (synonym types)
Date Mon, 07 Oct 2013 12:40:46 GMT

    [ https://issues.apache.org/jira/browse/DERBY-6340?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13788111#comment-13788111

Rick Hillegas commented on DERBY-6340:

Hi Dyre,

Thanks for continuing to button-down this spec. Some responses follow:

> Is DERBY-5901 the reason why the name must not conflict with a builtin
> function or aggregate?

Yes, that's right.

> Without the ability to specify <cast to source> you can create at
> most one alias for each builtin type in the same schema?

That's not my reading. The Standard lets you create multiple routines with the same schema-qualified
name provided that their argument signatures are different. Derby does not support this flexibility
with user-created routines, but that's a limitation we could lift with a little work. For
the SQL Standard rules, see part 2, section 4.28; in the 2011 edition, the relevant paragraph
is the last paragraph on page 98.

> 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?

Again, that's not my reading. I don't think that we need the <cast to source> clause.
The different distinct types will implicitly create <cast to source> functions which
have the same name but different argument signatures.


> 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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