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https://issues.apache.org/jira/browse/DERBY-3155?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13869461#comment-13869461
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Knut Anders Hatlen commented on DERBY-3155:
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The NPE goes away if I specify the target column names in the mergeInsert
clause, like this:
{noformat}
ij(CONNECTION4)> merge into t1 using t2 on t1.x = t2.x when matched then update
set y = -y when not matched then insert (x, y) values (t2.x, 42);
0 rows inserted/updated/deleted
WARNING 02000: No row was found for FETCH, UPDATE or DELETE; or the result of a
query is an empty table.
{noformat}
According to the functional spec, the target column names are optional in the
mergeInsert clause.
> 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: MergeStatement.html, MergeStatement.html,
> MergeStatement.html, derby-3155-01-ac-grammar.diff,
> derby-3155-02-ag-fixParserWarning.diff,
> derby-3155-03-ae-backingStoreHashtableWithRowLocation.diff,
> derby-3155-03-af-backingStoreHashtableWithRowLocation.diff,
> derby-3155-03-ag-backingStoreHashtableWithRowLocation.diff,
> derby-3155-03-ah-backingStoreHashtableWithRowLocation.diff,
> derby-3155-04-ae-deleteAction.diff, derby-3155-04-af-deleteAction.diff,
> derby-3155-05-aa-triggerTransitionTableAsTarget.diff,
> derby-3155-06-aa-triggerTransitionTableAsSource.diff,
> derby-3155-07-ad-insertAction.diff, derby-3155-08-ah-updateAction.diff,
> derby-3155-09-aa-correlationNames.diff,
> derby-3155-10-aa-correlationNames.diff,
> derby-3155-11-ab-beforeTriggersCantFireMerge.diff
>
>
> 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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