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From "Knut Anders Hatlen (JIRA)" <j...@apache.org>
Subject [jira] Updated: (DERBY-4495) Add NATURAL JOIN syntax
Date Tue, 29 Dec 2009 08:58:29 GMT

     [ https://issues.apache.org/jira/browse/DERBY-4495?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Knut Anders Hatlen updated DERBY-4495:
--------------------------------------

    Attachment: natural_preview_v2.diff

Uploading a new preview patch that addresses the known issues with the first patch and also
adds some test cases. To get the correct expansion of asterisks, the natural join was transformed
to a USING join earlier, at the end of bindExpression(). Also, the transformation of a USING
clause to a join condition was modified so that it generates a valid join clause if there
are no common columns (otherwise it would generate an AndNode with no children and cause a
NullPointerException).

One new problem was found: Combining NATURAL with other join operators may fail with a NullPointerException.
For example, this query fails:

  SELECT * FROM T1 CROSS JOIN T2 NATURAL JOIN T3

The problem appears to be that the RCL of the CROSS JOIN operation has not been instantiated
when the USING clause for the NATURAL JOIN operation is generated. The RCL is actually still
null when the expansion of asterisks happens, so simply delaying the generation of the USING
clause until we need it doesn't prevent the NPE (we need to know the common columns to expand
asterisks correctly).

> Add NATURAL JOIN syntax
> -----------------------
>
>                 Key: DERBY-4495
>                 URL: https://issues.apache.org/jira/browse/DERBY-4495
>             Project: Derby
>          Issue Type: Improvement
>          Components: SQL
>    Affects Versions: 10.6.0.0
>            Reporter: Knut Anders Hatlen
>            Assignee: Knut Anders Hatlen
>            Priority: Minor
>         Attachments: natural_preview.diff, natural_preview_v2.diff
>
>
> It would be nice if Derby supported the NATURAL JOIN syntax (feature F401-01 in SQL:2003).

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