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From "Andrew McIntyre (JIRA)" <j...@apache.org>
Subject [jira] Commented: (DERBY-1623) Add ANSI TRIM implementation
Date Sat, 14 Apr 2007 05:02:15 GMT

    [ https://issues.apache.org/jira/browse/DERBY-1623?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12488848

Andrew McIntyre commented on DERBY-1623:

Hi Manish,

SQL99 does list LEADING, TRAILING, and BOTH as reserved words. Also, I don't think that making
them non-reserved keywords is going to be possible with the current parser implementation,
since if you place them in the non-reserved list, you will necessarily get a conflict between
the first token (in my suggestion, from ansiTrimType()) and the expansion of the non-optional
token - in my example, characterValueExpression() - which can be a columnReference and thus
just an identifier. The rule for identifiers currently includes the list of non-reserved keywords,
which I suspect would lead to a conflict in any implementation which checks non-reserved keywords
against identifiers. While there is a possibility for impact to existing applications, I'm
wondering how serious the impact would be since the SQL99 standard has the keywords in question
listed as reserved.

As for the case expression not working, it doesn't appear that SQL99 includes case expressions
in <character value expression> or <character value function>, but it is very
likely that I'm missing something in the spec. If such expressions in column references are
allowed, and this is something other databases support, we should give it consideration.

I'd love to hear more feedback, and I'll dig some more into the standards to see what I can

> Add ANSI TRIM implementation
> ----------------------------
>                 Key: DERBY-1623
>                 URL: https://issues.apache.org/jira/browse/DERBY-1623
>             Project: Derby
>          Issue Type: Improvement
>          Components: SQL
>            Reporter: Emmanuel Bernard
>         Assigned To: Manish Khettry
>         Attachments: 1623-parser-guess.diff, AnsiTrimTest.java
> JPA is requiring databases to support this ANSI feature esp the ability to chose the
trimmed character
> TRIM([ [ LEADING | TRAILING | BOTH ] [ chars ] FROM ] str)

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