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From "Rick Hillegas (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (DERBY-3155) Support for SQL:2003 MERGE statement
Date Fri, 11 Apr 2014 12:50:17 GMT

    [ https://issues.apache.org/jira/browse/DERBY-3155?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13966457#comment-13966457
] 

Rick Hillegas commented on DERBY-3155:
--------------------------------------

Thanks for finding this bug, Knut. What distinguishes this case from the case tested in MergeStatementTest
is the use of a column from the transition table in the result expression for the column being
changed by the MERGE statement. The trigger definition succeeds if I change "set y = x" to
"set y = 2 * y":

{noformat}
connect 'jdbc:derby:memory:db;create=true';

create table t1(x int);
create table t2(y int);

-- fails
create trigger tr1 after insert on t1
referencing new table as new
merge into t2
using new on x = y
when matched then update set y = x;

-- succeeds
create trigger tr2 after insert on t1
referencing new table as new
merge into t2
using new on x = y
when matched then update set y = 2 * y;
{noformat}


> 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, 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, derby-3155-12-aa-canOmitInsertColumnList.diff,
derby-3155-13-aa-allowSystemAndTempTables.diff, derby-3155-14-aa-replaceCorrelationNamesOnLeftSideOfSETclauses.diff,
derby-3155-15-aa-replumbMergeResultSetCleanup.diff, derby-3155-16-aa-treatCurrentRowLocationNodeLikeBaseColumnNode.diff,
derby-3155-17-aa-serializingRowLocations.diff, derby-3155-18-aa-basicView.diff, derby-3155-19-aa-forbidSubqueriesInMatchedClauses.diff,
derby-3155-20-aa-reworkColumnMatching.diff, derby-3155-21-ac-cleanupAndForbidSynonyms.diff,
derby-3155-22-ad-testIdentifiersOnLeftSideOfSetClauses.diff, derby-3155-23-aa-forbidDerivedColumnLists.diff,
derby-3155-24-aa-supportParameters.diff, derby-3155-25-aa-parametersAsInsertValues.diff, derby-3155-26-aa-copyRowLocationForIndexScans.diff,
derby-3155-27-aa-adjustMatchingRefinements.diff, derby-3155-28-aa-cardinalityViolations.diff,
derby-3155-29-aa-missingSchema.diff, derby-3155-30-ab-moreCorrelationNames.diff, derby-3155-31-aa-deletePrivs.diff,
derby-3155-32-aa-newTestFunction.diff, derby-3155-33-ab-insertPrivs.diff, derby-3155-34-aa-updatePrivs.diff,
derby-3155-34-ab-updatePrivs.diff, derby-3155-35-aa-allPrivsTest.diff, derby-3155-36-aa-lockModeComment.diff,
derby-3155-37-aa-printSubNodes.diff, derby-3155-38-aa-datatypes.diff, derby-3155-39-aa-fixBuild.diff,
derby-3155-40-aa-bigLobs.diff, derby-3155-41-aa-nullGeneratedColumns.diff, derby-3155-42-aa-triggersAndGeneratedColumns.diff,
derby-3155-43-aa-eliminateDuplicateColumnRefs.diff, derby-3155-44-aa-lobsInTriggers.diff,
derby-3155-45-aa-serialization.diff, derby-3155-46-aa-deferredDeletes.diff, derby-3155-47-aa-collations.diff,
derby-3155-48-aa-indexScan.diff, derby-3155-49-aa-cleanup1.diff, derby-3155-50-aa-revampDeleteThenRows.diff,
derby-3155-51-aa-cleanup2.diff, derby-3155-52-aa-upgrade.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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