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https://issues.apache.org/jira/browse/DERBY-3155?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Rick Hillegas updated DERBY-3155:
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Attachment: derby-3155-02-ag-fixParserWarning.diff
Attaching derby-3155-02-ag-fixParserWarning.diff. This patch removes the
spurious comma separating WHEN [ NOT ] MATCHED clauses in the grammar. I am
running tests now.
This addresses two problems noted by Knut:
o You can't issue a MERGE statement with multiple WHEN [ NOT ] MATCHED clauses
using the grammar described by the functional spec.
o If you compile verbosely, you see the following warning during parser
generation:
[java] Note: UNICODE_INPUT option is specified. Please make sure you create the
parser/lexer using a Reader with the correct character encoding.
[java] Warning: Choice conflict in (...)* construct at line 8313, column 31.
[java] Expansion nested within construct and expansion following construct
[java] have common prefixes, one of which is: ","
[java] Consider using a lookahead of 2 or more for nested expansion.
I had planned to roll this fix onto a patch with more functionality, but that
patch is taking longer to write than I originally thought. So I'm submitting
this small change by itself.
Touches the following file:
M java/engine/org/apache/derby/impl/sql/compile/sqlgrammar.jj
> Support for SQL:2003 MERGE statement
> ------------------------------------
>
> Key: DERBY-3155
> URL: https://issues.apache.org/jira/browse/DERBY-3155
> Project: Derby
> Issue Type: Improvement
> Components: SQL
> Reporter: Trejkaz
> Assignee: Rick Hillegas
> Labels: derby_triage10_10
> Attachments: derby-3155-01-ac-grammar.diff,
> derby-3155-02-ag-fixParserWarning.diff, MergeStatement.html,
> MergeStatement.html, MergeStatement.html
>
>
> A relatively common piece of logic in a database application is to check for
> a row's existence and then either update or insert depending on its existence.
> SQL:2003 added a MERGE statement to perform this operation. It looks like
> this:
> MERGE INTO table_name USING table_name ON (condition)
> WHEN MATCHED THEN UPDATE SET column1 = value1 [, column2 = value2 ...]
> WHEN NOT MATCHED THEN INSERT column1 [, column2 ...] VALUES (value1 [,
> value2 ...])
> At the moment, the only workaround for this would be to write a stored
> procedure to do the same operation, or to implement the logic client-side.
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